Modular Ceiling Construction

Abstract

A modular grid system provides a skeletal framework for a ceiling composed of acoustical tile or the like. The main runners of the grid are identical, elongated channels each having a slotted base and a guide track formed therein. The main runners are interconnected to form a rectangular grid by connectors having a central portion formed with a hanger element serving as a point of attachment for suspending the grid and stub channel portions adapted to interfit with the elongated channel members in an interlocking relation. Portable partition walls may conveniently be bolted to the grid through the slotted base channels and utility conduits may likewise be passed through these slots without defacing the ceiling. An elongated filler or trim strip of flexible material is provided for selective insertion into the guide track of the elongated channel members for concealing the slots therein, when desired. Other features are disclosed.

Description

INTRODUCTION

The present invention relates generally to ceiling constructions of the type composed of a mosaic of individual acoustical tile or the like, and, more particularly, is directed to a new and improved modular grid system providing a support structure for a ceiling of the foregoing type.

SUMMARY OF THE INVENTION

The ceiling support structure of the present invention is of a modular design, employing a minimum number of components of simple and economical construction. The components preferably interfit in interlocking relationship without the use of bolts or the like thereby to expedite assembly. Further to this end, each of the components is preferably symmetrical so that the worker need not concern himself with part orientation. The main runners of the grid system are slotted both to facilitate securance of portable partition walls to the ceiling grid and to provide passages for utility conduits, etc., without the need of drilling special holes and without in any way defacing the surface of the ceiling. A filler or trim strip is adapted for slidable insertion into a guide track in the base of each main runner channel to conceal the slot therein, when desired. Various other features contributing to a simple, economical, and easy to assemble system, yet one which is structurally rugged, are disclosed in full detail layer herein.

Briefly, the invention is certain broader aspects is directed to a modular grid system providing a support structure for a ceiling of the type including a plurality of individual ceiling tile each of predetermined lateral dimensions. The grid system includes main runner means comprising a plurality of elongated members of identical construction, each member being of a length related to the lateral dimensions of the ceiling tile and each being an elongated channel of U-shaped cross-section with identical opposed end portions. An elongated slot is provided in the base of each channel member and a guide track is formed in the channel base for receiving an longated, flat strip. Connector means for joining the main runner channels into a repetitive grid of redetermined unit dimension comprises a central portion and a plurality of stub channel portions integral therewith and each stub being of a generally U-shaped cross-section similar to that of the channel members. The identical end portions of the elongated channel members and the stub channel portions of the connector means are constructed and arranged for fitting together in an interlocking relationship to form the rectangular grid structure without the use of bolts or the like. A filler or trim strip means comprises a plurality of elongated, flat strips of flexible material for selective insertion into the guide tracks of the elongated channel members for concealing the slots therein.

Other broad and efined aspects of the invention are considered and disclosed and claimed herein.

The novel features of the present invention are set forth with particularity in the appended claims. The invention together with further objects and advantages thereof may best be understood, however, by reference to the following description taken in conjunction with the accompanying drawings in the several figures of which like reference numerals identify like elements and in which:

FIG. 1 is a perspective view, taken from above, of a ceiling construction embodying the present invention;

FIG. 2 is a view taken along lines 2--2 of FIG. 1 and illustrating one of the repetitive grids of the ceiling wherein there is mounted a light fixture;

FIG. 3 is an exploded, perspective view illustrating several of the components of the modular grid system of the invention and their manner of assembly;

FIG. 4 is a cross-sectional view taken along lines 4--4, FIG. 3;

FIG. 5 is an elevational view, partly broken away, of a preferred embodiment of the grid connector means of the modular grid system of the invention;

FIG. 6 is a cross-sectional view taken along lines 6--6 of FIG. 5 and wherein a sprinkler head has been installed in a central aperture of the connector means of FIG. 5;

FIG. 7 is an elevational view, partly broken away, of a preferred embodiment of a main runner member of the grid system of the invention;

FIG. 8 is a cross-sectional view taken along lines 8--8 of FIG. 7;

FIG. 9 is an elevational view illustrating the manner of assembly of a portable partition wall to the ceiling grid system;

FIG. 10 is a sectional view of the completed ceiling structure showing the partition wall securely bolted thereto;

FIG. 11 is a perspective view illustrating the manner in which an air diffuser assembly is associated with the modular grid system of the present invention to provide air circulation to the room below;

FIG. 12 is an exploded detail view of a portion of FIG. 11 and illustrating in further detail the manner of assembly of the air diffuser with the grid system;

FIG. 13 is a view of the underside of the ceiling in the final stages of assembly;

FIG. 14 is a cross-sectional view taken along lines 14--14 of FIG. 1;

FIG. 15 is an exploded view of an alternate embodiment of light fixture and associated fixture support assembly; and

FIG. 16 is a cross-sectional view taken along lines 16--16 of FIG. 15 subsequent to assembly of the various components.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there is generally illustrated a modular ceiling construction 10 according to the present invention. Ceiling 10 is of a type that is suspended a predetermined distance below an upper plane (not shown), as by wires or cables 12. The wires or cables 12 are connected at regularly spaced intervals to a modular grid system which, as will be explained, defines the skeleton framework of the ceiling. The body of the ceiling is, of course, composed of conventional acoustical ceiling tiles 14 of predetermined lateral dimensions that are supported by the grid system.

The plenum region between the ceiling 10 and the upper support plane (not shown) accommodates various utility lines such as the electrical and water conduits 16 and 18, respectively, as well as air circulation means including air diffusers 20 and their associated air inlet ducts 22. In order to provide electrical service to the rooms below, it is necessary that apertures be made in the ceiling 10 to pass the conduits 16. Similarly, apertures in the ceiling 10 are required to accommodate sprinkler heads which are connected to the main water conduit 18 by stub conduit sections 18a. Further, in order to provide fresh air circulation, additional apertures must be provided in the ceiling 10 adjacent the exit ducts (not visible in FIG. 1) of the air diffusers 20.

According to one feature of the invention and as will presently be explained in detail, the grid system of the ceiling 10 is of a repetitive or modular design and the individual elements are constructed in such a way as to accommodate the location and relocation of the various utility conduits and the air diffuser apparatus with relative ease and without defacing the visible surface of the ceiling or in any way impairing its structural integrity.

The plenum space above the ceiling 10 also accommodates a spaced array of recessed lighting fixtures 24. The fixtures 24 in the present embodiment are supported from the grid system of the ceiling 10 by conventional brackets 26. The fixtures 24 are likewise simply and easily installed without drilling special holes or the like and the fixtures may conveniently be relocated to any selected one of the repetitive units of the grid without in any way damaging the grid structure or the ceiling tile. Additionally, portable partition walls 27 may simply and easily be secured to the grid at predetermined spaced intervals and the location of these walls may be promptly changed without damaging the ceiling 10.

An exemplary unit of the grid as viewed from the underside of the ceiling 10 is illustrated in FIG. 2. The grid unit of FIG. 2 encloses a centrally disposed, recessed lighting fixture 24. In this regard, it will be observed that the four ceiling tile 28 occupying the space between the fixture 24 and the surrounding grid members are of a different configuration than that of the standard, rectangular ceiling tile 14. Specifically, the tiles 28 are of a generally trapezoidal configuration configured to form mitered joints along the lines of intersection of the adjacent tile.

The basic elements of the modular ceiling 10 and their manner of assembly may be appreciated in greater detail by reference to FIGS. 3-8. Specifically, as shown in FIG. 3, the grid system is composed of main runner means comprising a plurality of elongated members 30, connector means 32 for interconnecting the main runners 30 into a rectangular grid pattern and secondary runner means comprising a plurality of elongated T-shaped members 34. The secondary runners 34 are of identical construction with identical opposed end portions adapted for connection to respective ones of a pair of space opposed main runners at periodic intervals along the lengths thereof so as to divide the unit area grid formed by the main runners into a plurality of sub-areas. Each of the sub-areas corresponds in lateral dimensions to that of an individual ceiling tile 14. The foregoing three elements form the basic skeletal framework of the ceiling 10; two additional elements, namely, a cover plate 36 and a plurality of filler or trim strips 38 are provided to permit a selective concealing of the repunched apertures in the connector means 32 and the main runners 30, respectively.

Before considering FIG. 3 in further detail, it is appropriate to first refer to FIGS. 5-8 for a complete understanding of the construction of the connector means 32 and the main runner members 30. As shown in FIG. 5, the connector means 32 comprises a central portion 32a, and a plurality of stub channel portions 32b integral therewith. Each of the stub channel portions 32b is of a generally U-shaped cross-section similar to that of the main runner 30. The stub channel portions 32b are of geometry complementary to that of the main runners 32 so as to permit a predetermined interfitting of these parts.

A hanger element 32c is formed in the central portion of the connector means 32 so as to provide a point of attachment for the suspension wire or cable 12. Preferably, the hanger element 32c is formed as a struck-out tab from the central portion 32a and it is further preferred that such struck-out tab be dimensioned so as to provide an opening in the central portion of a size to comfortably recieve the threaded terminus of the water conduit stem 18a as shown in FIG. 6. A conventional water sprinkler head 40 is threadably secured to the terminus of the conduit section 18a and completely conceals the central aperture. Thus, water sprinkler heads 40 may be installed at periodic spaced intervals in the modular grid system without drilling of any special holes or the like.

The connector means 32 is itself of a relatively economical and rugged construction. The connector may be formed as a stamping from a single piece of metal, as is clearly seen in FIG. 5.

Each of the main runners 30 is of identical construction and is of a length related to that of the lateral dimensions of the ceiling tile 14. Preferably, each runner 30 is formed as an elongated channel of U-shaped cross-section with identical opposed end portions and having one or more elongated slots 30a, 30b formed in the base thereof. It is also preferred that the base of the channel members 30 be provided with a guide track 30c or receiving an elongated, flat strip. In order to provide a secure inter-fitting of the channel 30 and the connector means 32, the upper ends of the opposed leg portions of the channel 30 are return bent at 30d for locating and securing the complementary stub channel portions 32b of the connector means therewithin without the use of bolts or the like.

In the ceiling construction of the present invention, it is contemplated that the individual tile 14 be installed merely be laying them in place on the grid structure and that no fasteners of any sort be employed. To this end and in order to support the individual tile 14, the main runners 30 further include exterior flanges 30e on opposite exterior sides of the channel legs. The exterior flanges 30e are of a width to accommodate dimensional tolerances in the tile and/or grid structure while providing in all instances adequate support for the tile. The channel members 30 are manufactured from rugged gauge metal and may economically be formed as unitary metal stampings.

As previously indicated, the secondary runners 34 are adapted to be connected across a pair of space opposed main runners 30 at predetermined intervals along the lengths of such main runners. In order to facilitate location and assembly of such secondary runners to the main runners, the main runners 30 are provided with spaced indexing means, herein a series of spaced slots 30f in the vertical legs of the channel members 30. The purpose and function of these indexing slots 30f may be fully understood by returning to FIG. 3 and particularly considering the construction of the secondary runner means 34. Specifically secondary runners 34 are each of identical, elongate construction with identical opposed end portions. In this regard, the end portions of the runners 34 are notched members dimensioned to securely locate and seat in the complementary slots of the main runners 30. The body of the secondary runners 34 are of a T-shaped cross-section, providing lateral flanges for supporting the ceiling tile 14. The secondary runners 34 likewise may economically be manufactured by conventional metal stamping techniques.

With the foregoing explanation, the manner of assembly of the three primary components of the modular grid should now be apparent. Briefly, however, and with reference to FIG. 3, the end portions of the several main channel members 30 are slidably interfitted with corresonding stub portions of the connector means 32 so as to provide a secure interlocking of these members without the use of fasteners of any kind. Assembly is expedited and simplified by having the end portions of the main runners identical so that the assembler need not concern himself with part orientation. A like condition prevails with respect to the secondary runners 34. The notched ends of the secondary runners are merely inserted in the easily visible slots of the main runners, again without the use of any tools or particular skill on behalf of the assembler. The secondary runners 34 are, of course, omitted from those grid units wherein there is to be installed a light fixture.

The grid structure, as now assembled, is ready to receive the ceiling tile 14. The tiles 14 are installed by inclining each tile so as to permit its unimpeded passage upwardly through the aperture in which it is to be located and then by reorientating the tile coincident with the plane of the grid and lowering it into position of rest on the peripheral support flanges of the grid runners. In those instances where the apertures in the runners 30 and the connectors 32 are not functionally employed, they are concealed by trim strips 38 and cover plates 36. The manner of installation of these latter two items is fully explained later herein.

Referring now to FIG. 9, the procedure for securing a partition wall 27 to the ceiling grid system may be understood. As is shown, the hollow partition wall 24 is aligned beneath a preselected main runner 30 of the grid and the necessary utility lines such as the electrical conduit 16 are threaded through the slotted apertures in the base of the runner 30 and into the hollow interior of the wall 27. A series of bolt assemblies disposed at appropriately spaced intervals along the main runner 30, and identical to the exemplary bolt assembly 42 are provided for securing the partition wall 27 to the ceiling grid structure. The head of the bolt 42 is of a configuration for securely and nonrotationally seating in the guide track 30c of the channel member 30 with the shank of the bolt extending through the slot of the channel and a bolt receiving aperture in the top surface of the partition wall 27. A lock washer and nut are then secured to the threaded shank of the bolt assembly. No special holes are drilled in the channel member nor is the ceiling structure in any way defaced by installation of the partition wall 27. Likewise, relocation of the partition wall 27 may conveniently and easily be accomplished without damage to the ceiling structure.

The modular ceiling grid system of the invention also provides for convenient and simplified installation of the room air circulation apparatus, as now may be appreciated by reference to FIGS. 11 and 12. As shown in these figures, the lower end or exit duct of each air diffuser 20 is in the shape of an elongated rectangular channel of a nominal width slightly greater than that of the main runner channel 30. The interference fit that results on seating of the lower end of the diffusers 20 within the channel members 30 is ample to secure the diffusers in position and no further fasteners of any kind are required. The air entering the plenum of the air diffusers 20 through the entry conduits 22 exits along the elongated slot in the base of the air diffuser 20, which slot is aligned with that in the base of the channel 30, as is clearly illustrated in the drawings.

FIG. 13 depicts installation of a typical cover plate 36 and a trim strip 38. The trim strips 38 preferably are composed of a flexible metal and are dimensioned for slidable insertion into the guide tracks in the bases of the guide channel 30 to provide an aesthetically pleasing cover to conceal the slots in the channel. Similarly, the cover plate 36 functions to conceal the central aperture of the connector means 36 and complete the ceiling grid pattern. The cover plate 36 is provided with four flexible corner tabs which are foldable over the exterior flanges of the main runners 30 to secure the cover plate 36 in position. The cover plate 36 has embossments in the shape of a "plus sign" to coincide with the regress of the filler 38 thereby to accurately align and center the cover plate and give the appearance of a continuous filler. As with all other components of the modular grid assembly of the present invention, no special fasteners are required and the cover plate may conveniently and promptly be removed if, for example, it is later desired to install a sprinkler head at this grid intersection.

FIG. 14 illustrates the recessed light fixture 24 and particularly the manner in which the ceiling tile 23 are supported. In this regard and according to one facet of the invention, the light fixture 24 is provided with a peripheral flange 24a serving as a support ledge for one edge of the tiles 28. The opposed edge of the tiles 28 are supported on the exterior flanges of the runners 30. Thus, the tiles 28 are laid in place in a fashion similar to that of the tiles 14 and may be removed for access to the light fixture, etc., without tools and without in any way damaging the tile.

An alternate form of light fixture and associated support assembly is illustrated in FIGS. 15 and 16. As seen in the drawings, a fixture support means or coffer 44 is of a frusto-pyramidal configuration having exterior dimensions corresponding to the unit dimension of the rectangular grid. Thus, the coffer 44 securely seats on the support flanges of the surrounding grid runners 30. The coffer 44 is preferably formed of perforated or solid steel and is of a single piece unitary construction. The interior aperture dimensions of the coffer 44 are such as to snugly receive a conventional heat extracting light fixture 46 and to this end there is provided a peripheral ledge 44a about the interior of the central aperture of coffer 44 so that the light fixture as well as the coffer may quickly and easily be installed without the use of fasteners.

While particular embodiments of the present invention have been shown and described, it is apparent that various changes and modifications may be made, and it is therefore intended in the following claims to cover all such modifications and changes as may fall within the true spirit and scope of this invention.

Claims

I claim:

1. In a modular grid system for providing a support structure for a ceiling of the type including a plurality of individual ceiling tile each of predetermined lateral dimensions, the improvement comprising:

an elongated runner member of a length related to the lateral dimensions of said ceiling tile and adapted for interconnection with other runner members to form a rectangular grid structure of repetitive unit dimension, said elongated runner member being of a generally U-shaped cross-section with similar opposed end portions and further having an elongated slot structure in the base of said U-shaped member for defining an access opening of a dimension for passing utility conduits and the like, and with a guide track formed in said channel base for slideably receiving an elongated, flat strip;

and an elongated, flat filler strip composed of a non-apertured flexible material for selective insertion into said guide track of said U-shaped member from one end thereof and from the room side of the ceiling for location in a predetermined interlocking and fixed relationship with said runner member for totally concealing said slot structure in said elongated runner member.

2. The improvement of claim 1 in which said U-shaped member is formed of an integral sheet of metal and in which said guide track is comprised of a pair of opposed, generally Z-shaped folds in said channel base spaced from one another by a distance corresponding to the width of said filler strip and of a thickness between the top and bottom of said Z corresponding to the thickness of said filler strip.

3. A modular grid system providing a support structure for a ceiling of the type including a plurality of individual ceiling tile each of predetermined lateral dimensions and for accomodating installation, removal and rearrangement of utility conduits, partition walls and room outlets for air ventilation passages at any desired location in said grid system without defacing said grid system and without the drilling of special holes therein, said grid system comprising:

main runner means comprising a plurality of elongated members of similar construction and each member being of a length related to the lateral dimensions of said ceiling tile and each having elongated slot structure formed therein for defining access openings through the ceiling of a dimension for passing utility conduits and the like, for providing bolt receiving apertures and bolt seats for connection of partition walls to said members and for serving as room outlets for air ventilation passages and each of said members further having similar opposed end portions;

connector means for interconnecting said main runner members in interlocking relationship to form a rectangular grid structure of a predetermined, repetitive unit dimension;

and filler strip means comprising a plurality of elongated, flat generally rectangular strips of a non-apertured flexible material for selective affixation to said elongated members from the room side of said ceiling and in an interlocking and fixed relation therewith for totally concealing unused ones of said slot structures in said elongated members, each of said filler strips being selectively and individually insertable and removable from each of said interconnected main runner members independently of removal of any of said main runner members and connector means for permitting installation, rearrangement and removal of said utility conduits, air ventilation passages and partition walls within said grid system without defacement of said grid system and without the drilling of special holes therein.

4. A modular grid system providing a support structure for a ceiling of the type including a plurality of individual ceiling tile each of predetermined lateral dimensions and for accomodating installation, removal and rearrangement of utility conduits, partition walls and room outlets for air ventilation passages at any desired location in said grid system without defacing said grid system and without the drilling of special holes therein, comprising:

main runner means comprising a plurality of elongated members of similar construction, each member being of a length related to the lateral dimensions of said ceiling tile and each being an elongated channel of U-shaped cross-section with similar opposed end portions and further having elongated slot structure formed in the base of said channel or defining access openings in said ceiling of a dimension for passing utility conduits and the like, for providing bolt receiving apertures and bolt seats for connection of partition walls to said members and for serving as room outlets for air ventilation passages and with a guide track formed in said channel base for receiving an elongated flat strip;

connector means comprising a central portion and a plurality of stub channel portions integral therewith and each of said stub portions being of a U-shaped cross-section similar to that of said elongated channel members, said identical end portions of said elongated channel members and said stub channel portions of said connector means being constructed and arranged for fitting together in interlocking relationship to form a repetitive rectangular grid structure;

and filler strip means comprising a plurality of elongated, flat generally rectangular strips of a non-apertured, flexible material for selective insertion into said guide tracks of said elongated channel members from the room side of said ceiling for location in a predetermined fixed relationship therewith for totally concealing the unused ones of said slot structures in said elongated channel members, each of said filler strips being selectively and individually insertable and removable from each of said interconnected main runner members independently of removal of any of said main runner members, connector means and ceiling tiles for permitting installation, rearrangement and removal of said utility conduits, air ventilation passages and partition walls within said grid system without defacement of said grid system and without the drilling of special holes therein.

5. The modular grid system of claim 4 in which said central portions of each of said connector means include hanger members for providng regularly spaced points of attachment from which to suspend said rectangular grid structure.

6. The modular grid system of claim 5 in which said central portions of each of said connector means are in the form of flat plates and in which said hanger members are formed by striking tabs from said central portions of said connector means.

7. The modular grid system of claim 6 in which said tabs are of predetermined dimensions such that the apertures formed in said central portions upon striking said tabs are of dimensions to suitably accommodate water sprinkler heads.

8. The modular grid system of claim 7 and further including cover plates adapted for selective securance over said central portions of said connector means to conceal the apertures therein.

9. The modular grid system of claim 8 in which the elongated slot in the base of each of said plurality of channel members is of a dimension to suitably pass utility conduits and further in which each slot is sufficiently narrow relative to the transverse dimension of said channel base portion to provide a peripheral support flange about said slot whereby portable partition walls may be secured to said channel base portion by means of bolts seated in guide track along said channel base portion.

10. The modular grid system of claim 9 in which said grid system is adapted to support air circulation means of a type including a plurality of air diffuser structures each having an elongated, rectangular air exit duct formed by a pair of elongated side walls and in which the width of each of said elongated channel members is substantially equal to that of said diffuser exit duct for receiving said exit duct portion of said air diffuser structure within said elongated channel member in a securely interfitting relationship.

11. The modular grid system of claim 4 in which each of said plurality of elongated channel members of said main runner means further includes exterior flanges lying in a common plane with that of said channel base portion for providing a support surface for said individual ceiling tiles.

12. The modular grid system of claim 11 and further comprising secondary runner means including a plurality of elongated T-shaped members of identical construction and of lengths approximately equal to that of said U-shaped channel members of said main runner means for connection across a pair of space opposed channel members at predetermined spaced intervals therealong for subdividing the unit grid dimension defined by said elongated channel member of said main runner means into a plurality of equal sub-areas each of lateral dimensions equal to that of an individual one of said ceiling tile.

13. The modular grid system of claim 12 in which each of said plurality of elongated channel members of said main runner means is provided with an indexing structure at predetermined spaced intervals along its length for locating the end portions of each of said T-shaped members of said secondary runner means.

14. The modular grid system of claim 13 in which said main runner means, secondary runner means, connector means, and filler strip means are retained in assembled relationship exclusively through mutual interfitting with one another.

15. The modular grid system of claim 14 and further including a light fixture centrally supported within a rectangular grid unit defined by said main runner means, said light fixture further including a peripheral flange for providing a first support surface for said ceiling tiles and said exterior flanges of said channel members providing second support surfaces for said ceiling tiles.

16. The modular grid system of claim 4 and further including a light fixture of predetermined dimensions and a fixture supporting means comprising a frusto-pyramidal member having exterior dimensions corresponding to those of one unit of said repetitive rectangular grid structure and an interior aperture of dimensions for receiving said light fixture.

17. A modular grid system providing a support structure for a ceiling of the type including a plurality of individual ceiling tile each of predetermined lateral dimensions, comprising:

main runner means comprising a plurality of elongated members of identical construction and each member being of a length related to the lateral dimensions of said ceiling tile and each having identical opposed end portions;

connector means comprising stub portions of a geometry complementary to that of said end portions of said elongated members of said main runner means for mating therewith in interlocking relationship to form a rectangular grid structure of a predetermined, repetitive unit dimension and further comprising a central portion having a hanger element struck-out of the surface of said central portion for providing a point of suspension for said grid structure and for providing an aperture of corresponding size for passing utility conduits;

secondary runner means comprising a plurality of elongated members of identical construction and having identical opposed end portions and further having a geometry for mating with said elongated members of said main runner means in interlocking relationship to divide said unit dimension grid structure into a plurality of sub-areas equal to the lateral dimensions of said ceiling tile;

and cover plate means for selective securance over said centtral portion of each of said connector means to totally conceal the unused ones of said apertures.

18. The modular grid system of claim 17 in which said members of said main and secondary runner means and said connector means are maintained in assembled relationship exclusively through interfitting with one another.

19. The modular grid system of claim 18 in which each of said main and secondary runner means include support flanges for providing peripheral support for each of said ceiling tile.

20. The modular grid system of claim 19 in which said elongated members of said main runner means are each formed as channel members of a generally U-shaped cross-section and each have exterior support flanges extending along opposite sides of said channel member and in which said elongated members of said secondary runner means are each of a generally T-shaped cross-section.

21. The modular grid system of claim 20 in which said elongated channel members of said main runner means are provided with indexing structure at predetermined space intervals along their length for locating said elongated members of said secondary runner means.