US3846031A

US3846031A - Ceiling grid system expansion joint

Info

Publication number: US3846031A
Application number: US00240921A
Authority: US
Inventors: G Adams
Original assignee: Rollform Inc
Current assignee: Rollform Inc
Priority date: 1972-04-04
Filing date: 1972-04-04
Publication date: 1974-11-05
Anticipated expiration: 1991-11-05
Also published as: DE2316927A1; CA966269A; FR2179123A1

Abstract

A structural main beam for use in the supporting lattice or grid of a fire rated suspended ceiling comprising a longitudinally extending web having bulb and flange portions located along opposite upper and lower marginal edges thereof, and including coupling means at opposite longitudinal ends for expandably interlocking a pair of beams in end to end relationship. Thermal expansion of the beam is localized in the interlocking coupling means and in at least one deformable section formed by a pair of vertically oriented apertures or cut outs in the web, the apertures being disposed proximate each of the bulb and flange portions respectively to permit bending thereof whereby the integrity of the ceiling is substantially maintained when subjected to extremely high thermal stresses such as can occur during exposure to a fire.

Description

Nov. 5, 1974 Adams 3.496.690 2/l970 Jahn....

[ CEILING GRID SYSTEM EXPANSION 33 r. o b r A n n A S m a d We rh mm GM m JII- H 7 .l.

S .N .w A m w L D: NP. A R MO 5 6 m E n 3 WP HN MG 5 R O F 848,ll5 8 1970 C- zd' 52 BK. 5 [73] Assignee: Rollform Incorporated, Ann Arbor, I I J Primary Examiner-Thomas F. Callaghan Agent, or Firml-iarness, Dickey & Pierce Mich.

Apr. 4, 1972 [22] Filed:

Attorney,

ABSTRACT [21] Appl. No.; 240,921

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n o wfmm m m T08 61 h h Tw mam 5mm [56] References Cited UNITED STATES PATENTS g disposed proximate each of the bulb and flange ortions respectively to permit bending thereof by the integrity of the ceiling is substantially maintained when subjected to extremely high thermal stresses such as can occur during exposure to a fire.

12 Claims, 3 Drawing Figures S e r u t fl 6 P a e h t b e w e h t .m S t u o t U C r o S e r u t r e P a d ebP where 33 A A 6556 3 9559 8 .8 l. .l u/

. 7 7 n 00 00 u 2 2 m mmmmml u. n u U n uunnuunt mn n ye m m m U I nwe$t mo m mo [6 n r. i km .1 mmflnflwnm onkflaofln CZL-JHDJZ 4566000089 66666666 99999999 .llllllll. 26 26007 1 ll CEILING GRID SYSTEM EXPANSION JOINT BACKGROUND AND SUMMARY OF THE INVENTION This invention relates generally to fire rated ceilings, and more particularly to an improved structural main beam for use in the associated supporting lattice or grid structure therefore.

As is well known, when accoustical ceilings are suspended from a conventional ceiling or overhead structure, the air space defined therebetween provides insulation for resisting heat transfer and in the event of a fire is most valuable for limiting the fire to the space beneath the suspended ceiling. It is also well known however that when the grid or lattice system supportingthe suspended ceiling is subjected to substantial thermal stresses, the structural beams including both the longitudinal main beam and the cross beams'which form the supporting lattice, tend to twist and buckle. This occurrence has been found to lift and sometimes dislodge the heretofore supported ceiling panels thereby exposing the superstructure to the fire and thus allowing the fire to spread more rapidly than would otherwise be the case. In a fire rated ceiling, various means have been proposed to localize the thermal expansionof the lattice whereby the integrity of the suspended ceiling issubstantially retained or at least retained for anincreased time interval. The subject invention is addressed to a main structural beam for use in a fire rated suspended ceiling assembly which is adapted to functionally retain the integrity of such a ceiling. It is therefore the primary object of the subject invention to provide an improved structural main beam for a suspended ceiling assembly which is adapted to localize and control thermal expansion and thereby substantially maintain the integrity of the suspended ceiling during exposure to a fire. I

In the subject invention the thermally responsive structural beam includes a web portion having a continuous flange on one spaced marginal edge and a bulb or rolled over portion along an opposite marginal edge. A pair of vertically spaced rectangular apertures or cut outs are located adjacent the bulb and flange portions, respectively, and are adapted to provide localized deformation of the flange and bulb portion in response to longitudinal expansion of the beam. For purposes of supporting the ceiling panels and other ancillary associated structure, it is desirable that the deformable section be devised in such a manner as to obviate the need for additional bracing or reinforcing members for supporting the ceiling load. In beams requiring additional reinforcing members, the design of the beam itself becomes more complex and correspondingly more costly to produce. It is therefore a general object of the subject invention to provide a beam having a localized deformable section not requiring additional reinforcement to support normal ceiling loads thereby simplifying the design and fabrication thereof.

In another aspect of the invention the main structural beams are adapted to be connected in end to end relationship by means of an expandible interlocking coupling arrangement devised to provide expansion relief in response to exposure of induced stresses. It is therefore another object of the subject invention to provide an expandible interlocking coupling arrangement for longitudinally joining a pair of main beams in end to end relationship.

It is another object of the subject invention to provide an improved main beam for an accoustical ceiling construction that provides a positive fire barrier between the floor and the ceiling of an enclosed space.

It is still another object of the subject invention to provide an accoustical ceiling construction that accomplishes longitudinal expansion of the grid members of an accoustical ceiling grid system.

It is a further object of the subject invention to provide a main beam for a lattice structure adapted for supporting accoustical panels that maintain structural integrity over relatively high ambient temperature conditions.

It is still a further object of the subject invention to provide a structural main beam of the above character BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged fragmentary prospective view of a pair of main structural beams in accordance with the subject invention adapted for forming a part of a supporting lattice of a suspended ceiling and illustrated with a pair of fragmentary cross beams before assembly thereof;

FIG. 2 is an enlarged fragmentary prospective view of the end portions of the pair of main structural beams illustrated in FIG. 1 illustrating the pair of beams interlockingly connected;

FIG. .3 is an enlarged fragmentary prospective view of the structure illustrated in FIG. 1 with the cross beams assembled thereto and after the assembly has been exposed to a substantial thermal load; and

FIG. 4 is an enlarged, fragmentary plan view looking in the direction of the arrows 4-4 in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In a fire rated suspended ceiling, a plurality of main structural beams are generally located in spaced parallel relationship, with the spacing generally corresponding to an edge dimension of a ceiling panel such as an acoustic tile, a gypsum board, or the like and adapted to be supported by laterally extending flanges located on the lower end of each of the beam members forming the lattice. The space between adjacent main structural beams is likewise subdivided by means of suitable cross beams appropriately located on centers which accommodate the adjacent edge dimensions of the ceiling panels to be suspended. The cross beams are adapted to be supported at their extremities by the main beams and are usually located in perpendicular relationship thereto. As shall hereinafter be described, and in accordance with the subject invention, the cross beams are flexibly interlocked. in suitable slots located in the web of the main beams and adapted for maintaining the integrity of the system during a fire.

With reference now to FIG. 1 of the drawings a structural main beam is indicated generally at 10, the beam l0'being adapted for use in forming a supporting lattice for a fire rated suspended ceiling. The beam 10 is commonly referred to in the trade as a T-member because of its generally inverted T-shaped vertical cross crosssection and, as shown, the beam or T member is comprised of a vertically extending web 12, a ceiling panel supporting flange 16 which extends laterally from opposite sides of the web 12 and an enlarged bulb 14 of generally rectangular shaped cross-section. As illustrated, the member 10 is shown in abutting end to end relationship with an identical structural beam 10', the beam 10' having a web 12', a bulb 14' and a laterally extending flange 16'. For purposes of clarity, the beam 10' is designated by like numerals used to designate the beam 10 but with the addition of a prime suffix. In the subject invention the structural beams 10 and 10' are slidably held together and guided by an interlocking arrangement which permits the use of standard length beam members, e.g., 12 feet, in various multiples or parts thereof to accommodate different spans.

To form a supporting lattice for a suspended ceiling, the structural beam members 10 and 10' are installed in parallel rows spaced apart a distance substantially equal to or slightly greater than an edge dimension of a ceiling tile (not shown) to be used whereby parallel edges of the panels are supported in flanges, such as the flanges l6 and 16', respectively. The beams 10 and 10' include a plurality of spaced apertures 18 adapted to receive suitable hangers (not shown) for supporting the grid system from the superstructure, and spaced sets of vertically oriented slots 20, the latter being used for receiving tabs 22, for interconnecting

suitable cross beams

24 and 24, respectively to the member 10. The cross beams 24 and 24' also are generally inverted T- shaped in cross-section and each include web, bulb, and flange portions substantially identical to the web 12, bulb l4, and lateral flange 16 of the beam 10. Additional sets of apertures are longitudinally spaced in the web 12 of the beam 10 and are adapted to receive projecting tabs of other cross beams (not shown). The sets of apertures are preferably longitudinally spaced I flanges of the cross beams so that the grids system formed by the main structural beams and the cross beams define a substantially rectangular lattice. The

rectangular lattice together with ceiling panels supported thereon present an aesthetically pleasing and accoustically superior ceiling for the enclosure. The details of the interlocking relationship between the main

structural beams

10 and 10 and the cross beams 24 and 24' form no part of the present invention and are included herein for clarity. Reference may be had, however, to US. Pat. No. 3,396,997 for a detailed explanation as well as an illustration and explanation of the grid system formed thereby, the patent being assigned to the assignee of the subject invention and the grid system due to thermal expansion, the cross beams 24 and 24' can be permitted to expand in a manner described in US. Pat. No. 3,396,997 previously incorporated herein by reference. Correspondingly. the

main beams

10 and 10 also expand under the influence of thermal expansion and due to the substantially greater length thereof, the expansion must be controlled to retain the integrity of the lattice.

In the subject invention, the coupling means for interlocking the main structural beams 10 and 10' in end to end relationship are adapted to provide expansion relief. As best observed in FIG. 1, the end of the beam 10 includes a projecting web portion 28 spaced slightly outward from the plane of the web 12 and defining a vertical shoulder 27 therewith, and a generally rectan-' gularly shaped tab 30 which deflects slightly inward relative to the web 12' of the beam 10'. Moreover, a tab engaging aperture 34 is suitably located to the left of the end portion 28 and adapted for receiving a tab 30' as defined in the abutting end of the beam 10'. For ease in assembly and for obviating the need for additional reinforcement, when interlocking the beams 10 and 10', the tab 30 is convergentially tapered outwardly, the inner vertical dimension being substantially equal to the vertical dimension of the aperture 34. Thus it will be seen that the inner portion of the tab provides a retainer slide or guide for the beam assembly when engaged in the tab engaging aperture. The bulb sections, however, 14 and 14' of each of the beams 10 and 10', respectively, is suitably undercut and defines vertically extending shoulder portions 32 and 32', respectively, which normally provides a longitudinally extending void in the bulb portions when the beams are interconnected in end to end relationship. The beams 10 and 10' are interconnected by locating the

tabs

30 and 30 in the tab receiving apertures 34 and 34', respectively, and then suitably reversely folding over the tabs therethrough. As shall hereinafter be explained, the longitudinal distance between the shoulders 32 and 32', re spectively define the limits of a slidable expansion relief point, the operation of which will be hereinafter described in conjunction with the operation of the beam 10 when subjected to a fire.

ln'addition to the expansion provided by the interlocking coupling means, the main

structural beams

10 and 10 include, at least, one localized expansion joint whereby thermal expansion can be localized to a selective area or zone of the beam, and the integrity of the system can be maintained. To this end the web 12 of the beam 10 is seen to include a generally rectangular shaped cutout area or slot 36 which defines a continuous marginal strip 46 of substantially uniform width between the lower edge of the aperture and the flange 16. A V-shaped notch 38 formed in the strip substantially at the substantial at the midpoint of the lower edge of the aperture 36 extends downwardly toward the flange 16. A second elongated rectangular slot or cut out 40 of slightly longer longitudinal dimension and centrally disposed and spaced above the cut out 36 defines a continuous marginal strip 48 also preferably of substantially uniform width adjacent to the bulb 14. Preferably the bulb 14 includes suitable vertical suppression points or creases 44 oriented in accordance with the midpoint and end edges of the slot 40 to provide stress concentration points in the bulb 14 as shown generally in FIGS. 1 and 3 and in greatly exaggerated form in FIG. 4. The

rectangular cut outs

36 and 40 are adapted to permit lateral bending of the bulb 14 and of a section 42 of the web 12 disposed between the

slots

36 and 40 and downward bending of the flange 16 in response to thermal expansion of the beam 10.

In operation, when the beam is exposed to a fire, the flange 16 is subjected to the highest thermal loading due to its location in direct confrontation therewith. The bulb portion 14 located on the opposite vertical end of the beam however is exposed to a substantially less thermal loading due to its vertical position above the flange and generally speaking is only indirectly subjected to the high temperature source. With reference now to FIG. 3, the beam 10 is illustrated in its expansion relief state. More particularly it will be seen that the flange l6 buckles downwardly due to the eminence of the V-notch 38 disposed midway in the slot 36 providing stress concentration in the web 12 and more particularly described in the patent to Adams, US. Pat. No. 3,350,125, the patent also being incorporated herein by reference. The portion 42 on the other hand being located between the

slots

40 and 36 deforms laterally while the bulb portion 14 is deflected laterally but to a lesser extent due to less thermal loading. it will be noted, however, that the buckling is localized and that the beam will still retain the supported ceiling panels.

With reference to the right end of the beam 16 and as again illustrated with reference to FIG. 3, it will be seen that the flange l6 deflects upwardly in response to thermal expansion of the web 12 of the beam 10 to drive the shoulders 32 and 32' into abutting confrontation. Simultaneously the folded over tabs and 30 longitudinally and guidably slide along the outer surfaces of web 12 and 12' and provide a slip joint therebetween. Thus jamming relief at the juncture between the

beams

10 and 10 is adequately provided to at least partially relieve the thermal expansion of the beams 10 and 10' while maintaining the interconnection thereof.

In a preferred form of the beam 10, two expansion relief cut outs, each comprised of the

slots

36 and 40 are located inwardly a selective distance from each opposite longitudinal end of the beam 10. By having two expansion relief cut outs, the elongation is more evenly distributed in the beam and the structural characteristics and integrity is enhanced. Thus, the subject beam provides an improved grid system for a suspended ceilmg.

While it will be apparent that the preferred embodiment of the subject invention disclosed herein is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation, and charge without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

l. A controlled expansion beam for use in a ceiling grid system comprising:

a longitudinally elongatedweb having a lower flange adapted to support the marginal edge portion of a ceiling panel and an upper continuous bulb portion; and

means formed in said web intermediate the ends of said beam providing a controlled localized expansion relief section for said beam, said means including upper and lower longitudinally elongated apertures formed solely in said web one above the other and disposed in spaced relationship between said flange and said bulb portion, said apertures defining longitudinally extending upper and lower continuous marginal strips in the web along and adja- 5 cent to said bulb portion and said flange, said marginal strip located adjacent to said flange being of substantially uniform width and provided intermediate the ends thereof with only a single mediunly disposed notch means which extends downwardly from said lower aperture and terminates short of said flange for controlled downward buckling of said flange in response to longitudinal compressive forces applied to said beam.

2. The beam as recited in claim 1 wherein said bulb includes a plurality of creases proximate said upper aperture to facilitate lateral deflection of said bulb when said beam is compressed longitudinally.

3. The beam as recited in claim 1 wherein said upper and lower apertures further define a relatively thin strip 20 in said web between said apertures and said upper and lower marginal strips which is adapted to deflect laterally under longitudinal compression of said beam.

4. The beam as recited in claim 1 wherein a controlled localized expansion section is provided adjacent each end of said beam.

5. The beam as recited in claim 1 wherein the upper of said apertures is longer than said lower aperture.

6. The beam as recited in claim 1 including means located proximate, at least, one end of said beam for interlockingly connecting said beam in end to end relationship with a beam of similar configuration.

7. The beam as recited in claim 6 wherein said means includes a tabprojecting outwardly from said web, and an aperture located inwardly in said web relative to said tab.

8. The beam as set forth in claim 1 wherein said bulb portion is cut back at an end of said beam and including means at said end of said beam for connecting the lat- 40 ter in endwise butting relation to another similar beam, said means adapted to permit the interconnected ends of said beams to slide toward each other within limits defined at least in part by the cut-back of said bulb portion. 9. The beam as set forth in claim 8 wherein said means comprises a generally rectangular aperture adjacent to the mentioned end of said beam, and a longitudinal tongue on said end laterally offset from the plane of the web of said beam, said tongue adapted to extend alongside the web of said other similar beam and to be folded back through a similar aperture in said other beam, said tongue adapted further to slide longitudinally in said aperture and fitting snugly between the upper and lower edges thereof normally and during sliding movement thereof to hold said beam and said other beam substantially in alignment with each other. 10. A controlled expansion beam as recited in claim 1 further including a second beam substantially similar to the first recited beam and disposed in endwise butting relation with said first recited beam; and means providing a sliding interlocking connection between said beams, said means holding the butted ends of said beams rigidly together and in alignment with each other while permitting said ends to 7 8 crush together when said beams are compressed ening the beams so that they are likely to be damlongitudinally as under thermal expansion, the bulb aged by normal handling. portions of both beams being cut back and spaced 12. A pair of controlled expansion beams as set forth apart at the butted ends of the beams to facilitate in claim 10 wherein said means comprises crushing together of said beams and the cutback a generally rectangular aperture adjacent to the ends of said bulb portions adapted to interengage butted end of each beam, and to limit the extent to which said beams can crush a longitudinal tongue on the butted end of each beam together to relieve compressive forces in said extending alongside the other of said beams and beams. being folded back through the aperture in said 11. A pair of controlled expansion beams as set forth 1 other beam, in claim wherein each of said beams is provided adsaid tongues being longitudinally slidable in said apjacent each end thereof with an expansion relief section ertures when the butted ends of said beams crush of the type specified in claim 1, together and snugly fitting between the upper and said expansion relief sections and the cut-backs in the lower edges of said apertures to hold said ends in bulb portions of said beams being mutually collecalignment with each other normally and at least tively operable to absorb and relieve forces of longenerally while said beams are crushing together. gitudinal compression in said beams without weak-

Claims

1. A controlled expansion beam for use in a ceiling grid system comprising: a longitudinally elongated web having a lower flange adapted to support the marginal edge portion of a ceiling panel and an upper continuous bulb portion; and means formed in said web intermediate the ends of said beam providing a controlled localized expansion relief section for said beam, said means including upper and lower longitudinally elongated apertures formed solely in said web one above the other and disposed in spaced relationship between said flange and said bulb portion, said apertures defining longitudinally extending upper and lower continuous marginal strips in the web along and adjacent to said bulb portion and said flange, said marginal strip located adjacent to said flange being of substantially uniform width and provided intermediate the ends thereof with only a single medianly disposed notch means which extends downwardly from said lower aperture and terminates short of said flange for controlled downward buckling of said flange in response to longitudinal compressive forces applied to said beam.

3. The beam as recited in claim 1 wherein said upper and lower apertures further define a relatively thin strip in said web between said apertures and said upper and lower marginal strips which is adapted to deflect laterally under longiTudinal compression of said beam.

7. The beam as recited in claim 6 wherein said means includes a tab projecting outwardly from said web, and an aperture located inwardly in said web relative to said tab.

8. The beam as set forth in claim 1 wherein said bulb portion is cut back at an end of said beam and including means at said end of said beam for connecting the latter in endwise butting relation to another similar beam, said means adapted to permit the interconnected ends of said beams to slide toward each other within limits defined at least in part by the cut-back of said bulb portion.

9. The beam as set forth in claim 8 wherein said means comprises a generally rectangular aperture adjacent to the mentioned end of said beam, and a longitudinal tongue on said end laterally offset from the plane of the web of said beam, said tongue adapted to extend alongside the web of said other similar beam and to be folded back through a similar aperture in said other beam, said tongue adapted further to slide longitudinally in said aperture and fitting snugly between the upper and lower edges thereof normally and during sliding movement thereof to hold said beam and said other beam substantially in alignment with each other.

10. A controlled expansion beam as recited in claim 1 further including a second beam substantially similar to the first recited beam and disposed in endwise butting relation with said first recited beam; and means providing a sliding interlocking connection between said beams, said means holding the butted ends of said beams rigidly together and in alignment with each other while permitting said ends to crush together when said beams are compressed longitudinally as under thermal expansion, the bulb portions of both beams being cut back and spaced apart at the butted ends of the beams to facilitate crushing together of said beams and the cutback ends of said bulb portions adapted to interengage to limit the extent to which said beams can crush together to relieve compressive forces in said beams.

11. A pair of controlled expansion beams as set forth in claim 10 wherein each of said beams is provided adjacent each end thereof with an expansion relief section of the type specified in claim 1, said expansion relief sections and the cut-backs in the bulb portions of said beams being mutually collectively operable to absorb and relieve forces of longitudinal compression in said beams without weakening the beams so that they are likely to be damaged by normal handling.

12. A pair of controlled expansion beams as set forth in claim 10 wherein said means comprises a generally rectangular aperture adjacent to the butted end of each beam, and a longitudinal tongue on the butted end of each beam extending alongside the other of said beams and being folded back through the aperture in said other beam, said tongues being longitudinally slidable in said apertures when the butted ends of said beams crush together and snugly fitting between the upper and lower edges of said apertures to hold said ends in alignment with each other normally and at least generally while said beams are crushing together.