US3918354A

US3918354A - Suspended ceiling air distribution arrangement

Info

Publication number: US3918354A
Application number: US428117A
Authority: US
Inventors: Robert R Lambert
Original assignee: Wehr Corp
Current assignee: Venturedyne Ltd
Priority date: 1973-12-26
Filing date: 1973-12-26
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11

Abstract

A linear air plenum formed of duct board (generally a thickness of fiber glass) is connected to an elongated support pan. An elongated opening is provided in the pan and an arrangement of walls depends from the underside of the pan at the opening to form a collar registering with an air bar which includes diffuser elements and defines a slot in a suspended ceiling. Alternatively, a diffuser assembly is attached to the pan at the elongated opening in which case the slot is defined by an air track and the pan carried diffuser registers with the air track. In transverse cross section the air plenum is in the form of a polygon. The duct board is one-piece and relieved at the fold lines to facilitate folding to form the air plenum. The pan engages the air plenum, when so folded, to hold the duct board folded. The pan-air plenum combination is used in a ceiling having a series of main and cross runner T-bars; a number of such pan-air plenum combinations are connected end-to-end and arranged parallel to one of the series of cross runners or main runners and at right angles to and extending across the other. The length of the pan-air plenum combinations and the attached collar, or diffuser, are related to the module upon which the ceiling is constructed. Pivotal extractor blades are pivotally supported in the pan opening to direct air from the plenum through the air track or air bar. The pans are spaced above the main runners thereby providing alternating air supply and return areas.

Description

United States Patent [191 Lambert 1 Nov. 11, 1975 1 SUSPENDED CEILING AIR DISTRIBUTION ARRANGEMENT [75] Inventor:

[52] US. Cl 98/40 D; 98/40 C; 98/114 [51] Int. Cl. F24F 7/00 [58] Field of Search 98/40 R, 40 D, 40 DL, 40 C,

[56] References Cited UNITED STATES PATENTS 3,319,558 5/1967 Bodian 98/40 D 3,352,076 11/1967 Jones v 98/40 D 3,353,472 11/1967 Lee et a1 98/40 D 3,383,999 5/1968 Fragnito et a1. 98/40 D 3,411,425 11/1968 Lambert 98/41 R 3,420,439 l/l969 Meckler 98/40 DL 3,601,033 8/1971 Lambert 3,690,243 9/1972 Lambert 3.757.667 9/1973 Lambert 98/40 D Primary E.\'aminerWilliam E. Wayner Assistant E.rmninerl-lenry C. Yuen [57] ABSTRACT A linear air plenum formed of duct board (generally a thickness of fiber glass) is connected to an elongated support pan. An elongated opening is provided in the pan and an arrangement of walls depends from the underside of the pan at the opening to form a collar registering with an air bar which includes diffuser elements and defines a slot in a suspended ceiling. Alternatively, a diffuser assembly is attached to the pan at the elongated opening in which case the slot is defined by an air track and the pan carried diffuser registers with the air track. In transverse cross section the air plenum is in the form of a polygon. The duct board is one-piece and relieved at the fold lines to facilitate folding to form the air plenum. The pan engages the air plenum, when so folded, to hold the duct board folded. The pan-air plenum combination is used in a ceiling having a series of main and cross runner T- bars; a number of such pan-air plenum combinations are connected end-to-end and arranged parallel to one of the series of cross runners or main runners and at right angles to and extending across the other. The length of the pan-air plenum combinations and the attached collar, or diffuser, are related to the module upon which the ceiling is constructed. Pivotal extractor blades are pivotally supported in the pan opening to direct air from the plenum through the air track or air bar. The pans are spaced above the main runners thereby providing alternating air supply and return areas.

15 Claims, 6 Drawing Figures U.S. Patent Nov. 11, 1975 Sheet 1 014 3,918,354

U.S. Patent Nov. 11,1975 Sheet 3 of4 3,918,354

SUSPENDED CEILING AIR DISTRIBUTION ARRANGEMENT BACKGROUND OF INVENTION In discussing this invention reference has been, and

will be, made to a slot, an air bar, and an air t rack.'A' slot is an elongated, linear opening generally 1 inch to 2 inches wide, in a suspended ceiling defined between,

for example, the extremities of spaced ceiling support I members such as inverted T-bars. An air bar is a linear air diffuser, incorporating a means of pattern control and including as part of its assembly the support mem{ bers (inverted T-bars) forming the slot. An air track is the same as the air bar but does not include the pattern control, a separate diffuser being used in association with the air track to provide pattern control. Various air plenum constructions, diffuser constructions, and combinations thereof have been provided in the past. Examples of such constructions can be found in various US. patents issued to Robert R. Lambert, namely US. Pat. Nos. 3,227,063, 3,577,904, 3,601,032, 3,601,033, 3,690,243, 3,748,998; and

This invention is concerned with such constructions and the problems presented thereby.

SUMMARY OF rNvE TroN Some of the general objects of this invention are to provide an air delivery arrangement which is simple to assemble on site, provides versatility :in available air supply and return combinations, and which provides for efficient and economical shipping of the-basic elements of the air delivery arrangement.

For the achievement of these and "other objects-this invention proposes a combination including a generally elongated, linear basic pan to which an airplenum is connected. An elongated opening is provided in the pan and has a length which is less than the overall length of the pan thereby providing a pan which is closed except for that opening. The pan is spaced from the ceiling support members and the arrangement of the opening and the closed pan areas cooperate in providing supply and return areas the ceiling.

The pan-air plenum combination is used in a suspended ceiling. A slot is defined in the-ceiling and the pan opening is arranged in alignment with' the slot,with means being provided at the pan opening for registry with the slot so that air passing through the opening discharges through the slot. Preferably, the length of the pan opening is lessthan that of the slot so that the portion of the slot adjacent that registering with the pan opening communicates with a closed portion ofthe pan and can be used to provide an air return.

Preferably, the plenum is in the shape ofa polygon in transverse cross section. The plenum is formed from a one-piece duct member relieved at the fold linesto facilitate folding at the job site while permitting the duct member to be shipped flat. The pan is provided with means for engaging the duct board. after it is folded to hold the duct board on the pan in itsfolded shape. The duct board formed plenum is open at the pan opening so that air delivered into the plenum passes through the opening.

Preferably, a plurality of pans so constructed and with attached air plenums are arranged end-to-end along a ceiling slot to provide an elongated continuous air plenum. The ceiling includes a pattern of ceiling support members and the length of the pan. its opening, and the length of the air plenum are related to the module on which the ceiling is constructed.

The means connected at the pan opening, or opening's, can be in the form of a collar engaging an air bar which defines the slot. Alternatively the means can be a diffuser assembly, including its own pattern control, and engages an air track which defines the slot.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the embodiments shown in the drawings, in which:

FIG/1 is a perspective view partially exploded of an air plenum-pan combination;

FIG. 2 is a side elevation of the arrangement of FIG. 1;

FIG. 3 is a section view taken generally along lines 3-3 of FIG. 2;

FIG. 4 is a section view taken generally along lines 44 of FIG. 2;

FIG. 5 isa partial section view of an alternative embodiment of the invention;

FIG. 6 is a perspective view of a duct board section before it is folded into the air plenum shape; and

FIG. 7 is a perspective view partially exploded of yet another alternative embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS With particular reference to FIG. 1 of the drawings, anair delivery assembly 10 is illustrated as including three'airplenu'm

duct sections

12, 14, and 16 made up of conventional foil covered duct board (generally a thickness of fiber glass). The air plenum duct sections are joined by tape strips 11 to define a continuous plenuni chamber 17 and are connected to support

pans

18, 20, and 22. The construction of the support pans and their connection to the plenum sections will be described more completely hereinafter. The ends of the plenum formed by plenum duct sections 12, I4, and 16, and partially by

pans

18, 20, and 22, are closed by end plates 24 and 26 which again are connected to their respective plenum sections 12 and 16 by tape strips 11 and may be further fastened to the duct board by machine screws 13 extending through horizontal portion 15 0f the ends and into

pans

18 and 22. Sheet metal collar 28 is suitably attached to plenum section 14 at opening 30 and will accept a flexible duct so that air from a central air supply can be admitted into the plebar define a slot in the ceiling. Weir

members

38 and 40 in the form of nested channel shaped members extend the length of the air bar and are positioned between U-shaped

retainers

42 and 44, a pair of such retainers being provided at the opposite ends of the air bar but only one pair being illustrated in FIG. 3. The \veir members are held in the air bar but are free to move horizontally relative to each other and T-bars 32 and provides pattern. and to some degree volume, control of air discharging from the air bar. The ends of the air bar are closed by end plates 39 only one of which are illustrated in the drawings, i.e. FIG. 3. The construction, connection, and function of

weirs

38 and 40 are more completely described in Robert R. Lamberts US. Pat. Nos. 3,41 1,425 and 3,444,801 and should additional description be necessary, reliance is hereby placed on those patents. It is believed, however, that the above description is sufficient for purposes of understanding this invention.

The air bar assembly just described provides an air diffuser and incorporates its own pattern control arrangements, i.e. the nested weirs.

In accordance with conventional practice, slot 100 is generally continuous along the length of the ceiling, i.e. parallel to the main runners and can be either 1 inch or 2 inches or whatever width is desired although 1 inch and 2 inch slots are most standard.

FIG. 5 illustrates an alternative arrangement for providing the slot in the suspended ceiling. In this arrangement, main runners are again provided and a pair of inverted T-bars 46, parallel to and having the same construction as the main runners, are positioned adjacent each other but spaced such that their horizontal flanges 48 define the slot 102 which can have the same dimension as slot 100 as desired. This arrangement, i.e. the inverted T-bars 46 which do not include their own pattern control arrangement is an air track.

In both of the just described arrangements, i.e. the air bar or air track, the conventional ceiling tile 36 is supported between the standard main runners and the inverted T-bars 32 which make up either the air track or air bar.

Returning now to FIG. 3 wherein the slot is defined by the air bar assembly, the construction of the pan to cooperate with the air bar in providing air supply, will be described. The description of one pan will suffice for

pans

18 and 22 which are identical in construction to pan 20. Pan 20 includes a planar surface 21 terminating in

longitudinal sides

58 and 60 which are turned up to provide upwardly extending flanges, and also includes ends 23 and 25 (see FIG. 1). Spaced inwardly of these

sides

58 and 60 but parallel thereto, are a second pair of upstanding flanges 50 and 54 which terminate in angled lip 52 and 56 respectively. As illustrated, flanges 50 and 54 are cut from the basic pan and formed upwardly to leave an opening 62 therebetween. Except for opening 62, pan surface 21 is otherwise closed. A plurality of extractor blades are positioned in the opening 62. The plenum chamber 17 has open communication with opening 62, i.e. air flowing into the plenum chamber communicates directly with opening 62 for passage through that opening into the air bar or air track depending on the embodiment. The purpose of these extractors is to insure proper direction of the air delivered to the air plenum chamber into the air bar or diffuser 39. More specifically, air under pressure delivered into the air plenum chamber 17 will have a tendency to continue along a path parallel to the longitudinal axis of the air plenum, the extractors turn the air flow generally vertically for passage (in FIG. 3) through the air bar and slot 100.

Structurally, a plurality of extractor blades 64, five as illustrated in FIG. 1, are supported between

walls

68 and 70 spot welded to flanges 50 and 54. Each of the extractors includes a pair of tabs 65 at the opposite sides thereof. These tabs are connected to

walls

68 and 70 by pins 72 which form horizontal axis about which the extractors can be pivoted to vary the vertical orientation of extractor blades relative to air flow in the plenum. The extractors being pivotahle can vary the direction of air, i.e. vertical, all at the same angle to the horizontal, and at angles to the horizontal which are relatively divergent. This adjustability as to the angle at which air can be directed into the slot also results in adjustability of throw and spread of air in the room being serviced and all at a substantially constant volume of supply (cfm).

Shoulders 74 and 76 are provided in

walls

68 and 70 and are adapted to rest atop T-bars 32 thereby registering the air plenum opening 62 with the air bar. Springs 78 and 80 connected to

walls

68 and 70 hold the air plenum-pan combination assembled onto the air bar.

In the embodiment of FIG. 5, where the slot 102 is provided by an air track which does not include its own pattern control arrangement, a diffuser separate from the air track must be provided. In this embodiment, the pivotal extractors 64 are supported between the

upper portions

77 and 79 of side walls 82 and 84 of diffuser assembly 81. For in this embodiment, in contrast to that of FIG. 3, a collar does not extend from the underside of the pan but instead a diffuser assembly 81 and it defines the outlet opening 62'. Side walls 82 and 84 of the diffuser have horizontal extensions 83 each of which is spot welded to the underside of pan 20. Side walls 82 and 84 extend downwardly for engagement with horizontal flanges 48 of inverted T-bars 46 and nested weirs 138 and 140 are supported between walls 82 and 84 in the same manner as described in connection with FIG. 3. That is, retainer channels similar to 42 and 44 are provided at the opposite ends of the diffuser. Again, the opposite ends of the diffuser are closed by end plates 85 only one of which is illustrated in FIG. 5.

With reference to FIG. 2, it can be seen that the air bar assembly 39, and also the diffuser assembly 81, are of limited length relative to the length of

pans

18, 20, and 22 and

air plenums

12, 14, and 16. As illustrated, the lengths of the air bar assemblies, and the air track assemblies is generally equal to the distance between adjacent cross T-bars 41 thus providing spaced air supply areas above

slot

100, or 102.

With this arrangement, it is relatively simple to provide for air return, since openings 62 are the only openings in the pans and the pans are otherwise closed. Namely, those areas of the pans overlying those portions of the slot adjacent to or between adjacent air bar or air track, assemblies are closed can be used to provide for return air into the attic between the suspended ceiling and the actual structural ceiling. The return air arrangement is illustrated in FIG. 4 and FIG. 2. As can be seen in the drawings, the pans are spaced from the upper ends of the main runners, and the cross runners. This leaves a space between the tops of the inverted T- hars and the pans through which return air entering through slot can pass into the attic. With reference to FIG. 4 it will be seen that pan 20 is closed above the slot 100 with a hat shaped retainer 86 spot welded to the top of the pan to receive and hold air plenum duct section 14. As illustrated, the return air passage includes nested

weir

38 and 40 supported between

channels

42 and 44 in the same manner as in the air bar construction-The purpose of the nested weirs in the return air assembly is merely for aesthetics in that they block the direct line of sight through slot 100 into the attic. Accordingly, although an air bar assembly is illustrated, a more simple baffle arrangement could be utilized at the air return areas. The air bar assembly does have the advantage of affording a measure of damper control for return air.

With this arrangement and as illustrated in FIG. 2, it can be seen that alternating air supplies and air returns 39 and 51 are provided. It will also be appreciated that the arrangement of air supply and return can be varied as desired merely by varying the relative position of the pans and a return area can be completely eliminated by removing the return air bar assemblies 51, and replacing it with a blank off above slot 100. Thus, this overall combination of air plenum and basic support pan construction results in extreme versatility with simplicity of construction.

In order to provide for economical shipping of the principal or major space occupying element of the overall air plenum-pan combination (the duct board), specific duct board construction is provided and illustrated in FIG. 6. In FIG. 6, duct board 14 has been laid out flat and is shown as including relieved portions 90 in the form of cut V-shaped notches extending the length of the duct board. These relieved areas are actually the lines along which the folds are to be made to resultin the general rectangular shape of the air plenum sections. It will be appreciated that the same basic relieved notch construction can be utilized to provide any desired polygon shape.

With this construction of duct board, the duct board to be assembled into the

plenum sections

12, 14, and 16 can be shipped flat thereby occupying a minimum amount of shipping space for a given size of duct board. At the job site, the fold lines provide guides for the contractor who merely makes the folds along relieved portions 90. When the duct board is so folded, ends 92 result which are spaced from each other suchthat they rest on opposite sides of openings 62 overlying portions 94 of the pan abutting flanges 50 and 54 on one end and

flanges

58 and 60 on the other. Barbs 96 can be provided at selected points along

flanges

50, 54, 58, and 60 to hold the duct board in its assembled position. Also, strips of tape can be provided to further hold the assemblies in the polygon shape, i.e. strips 11 can extend not only around the joints of the duct board but also over the underside of the pan. As is perhaps best illustrated in FIG. 3, sections 92 of the duct board extend parallel to and overlie portions 94 of pan which extend between flanges 50- 58 and 54-60 and sections 92 are held securely between the opposed flanges and positioned by barbs 96.

A single air plenum can be utilized with a single pan if desired in which case its ends are closed. However, preferably, a plurality of such air plenum combinations are utilized as is illustrated in FIG. 1. Although only three air plenum sections have been illustrated in FIG. I, it will be appreciated that the air plenum sections can be multiplied to extend the complete length of a given room or the width between the building walls wherein they may then extend over a number of rooms. The advantage of this type of an arrangement is that. for example, where the assembled plenum combination extends over a number of rooms, crossed talk between rooms can be minimized by inserting a dam in the air plenum. This is accomplished by physically cutting through the air plenum sections, for example, l2, l4, l6, and inserting the dam in the cut section and taping the cut for seal purposes. Should the room walls ever be moved, the air delivery system can be modified to accommodate that move by merely relocating the dam in the same manner as just described, the previous cut, of course, being sealed. It will be appreciated that one main air supply inlet '28 is illustrated in FIG. 1 but where the length of the air plenum is increased appreciably, more than one such supply may be required, and would be required in the event that the same continuous length of plenum is extending over and servicing a number of different rooms.

Although the openings 62 are shown as being centered as they would be for an interior installation, they can be moved to accommodate perimeter installation or installation adjacent a light fixture.

FIG. 7 illustrates yet another alternative embodiment of this invention. In this embodiment the

basic pans

18, 20, and 22 having a construction identical to that illustrated and described in connection with either FIGS. 3 or 5 have air plenum boxes 98 associated with the upper sides thereof. These boxes each have a sole air supply opening 99 arid extend over only one of the openings 62 in the pan and there is no open communication between adjacent boxes as in

adjacent plenum sections

12, 14, and 16. This does, however, illustrate the versatility of the basic pan support which has been provided. Again, with this alternative embodiment, the areas adjacent to the openings 62 and which overlie either

slot

100 or 102 can be utilized to provide return air.

I claim:

'1. In combination in a suspended ceiling including a plurality of ceiling members, a plurality of ceiling support members, and means defining an elongated, linear slot in said ceiling, the improvement of an air delivery arrangement comprising, in combination,

means defining agenerally elongated, linear pan having marginal ends and longitudinal sides,

means defining an elongated opening in said pan having an extension generally parallel to the longitudinal axis of said pan, the length of said opening being less than the length of said pan and said pan being otherwise closed,

means defining a generally elongated, linear plenum member having wall portions defining a plenum chamber,

means connecting said linear plenum member to said pan with said plenum chamber having open communication with said opening and with a portion of said wall portions engaged with a portion of said pan,

means for delivering air to said plenum chamber for discharge through said opening,

means at said opening for connection to the means defining said slot along only a limited length of said slot corresponding generally to the length of said opening so that air will be discharged through said slot only through said limited length,

and said pan being spaced from said ceiling support members so that air delivered to said plenum chamber passes through said opening for discharge through said slot while the length of said slot adjacent that through which air is discharged underlies a closed extension of said pan and provides an air return.

2. The apparatus of claim 1 wherein said means connected at said opening comprises a diffuser assembly including,

spaced walls projecting laterally relative to said pan and defining a passage therebetween,

and pattern control means in said passage to deflect air flowing through said passage prior to discharge through said slot.

3. The apparatus of claim 1 wherein said means connected at said opening comprises a collar having spaced side and end walls projecting laterally relative to said pan and defining a passage therebetween through which air from said plenum chamber passes for discharge through said slot.

4. The apparatus of claim 1 wherein said pan includes means for engagement with said linear plenum member to connect said linear plenum member to said pan,

and wherein said opening is spaced inwardly from the longitudinal sides of said pan.

5. The apparatus of claim 1 wherein said linear plenum member is polygonal in transverse cross-section and is relieved at the fold lines thereof to accommodate the formation of the corners of said polygon shape,

and said pan including means for engagement with said linear member to connect said linear plenum member to said pan and hold said linear plenum member in said polygon shape.

6. The apparatus of claim 5 wherein said pan includes flanges along the longitudinal sides of said pan projecting from the basic plane of said pan, wherein means is provided along the longitudinal edges of said opening to provide flanges projecting from said basic plane in the same direction as said flanges along the longitudinal sides of said pan,

and wherein said linear plenum member wall portions include portions extending along said pan and engaged between said longitudinal side pan flanges and said opening flanges to hold said linear plenum member on said pan.

7. The combination of claim 1 wherein said ceiling support members comprise a first set of mutually parallel ceiling support members and a second set of mutually parallel ceiling support members arranged generally perpendicular to said first set,

including a plurality of said pans arranged end-to-end and all generally identical in construction and each having a length greater than the spacing between adjacent ones of said first set of ceiling support members,

including a plurality of said linear plenum members connected end-to-end parallel to said second set of ceiling support members,

and wherein at least two of said pans include said opening and said means connected at said opening, one opening and the means connected thereto spaced from the other opening and the means connected to it,

so that air delivered to said plenum chamber passes through said openings for discharge through longi' tudinally spaced portions of said slot while the lengths of said slot adjacent those longitudinally spaced slot portions through which air is discharged underlie closed extensions of said pans and provide air returns.

8. The apparatus of claim 7 wherein said means connected at said openings comprise diffuser assemblies including spaced walls projecting laterally relative to said pans and defining a passage therebetween,

and pattern control means in said passage to deflect air flowing through said passage prior to discharge through said slot. 9. The apparatus of claim 7 wherein said means connected at said openings each comprise a collar having spaced side and end walls projecting laterally relative to said pans to define a passage therebetween through which air from said plenum chamber passes for discharge through said slot.

10. The apparatus of claim 8 wherein the ceiling support members of said first set are equally spaced, 1

wherein said pans each have a length substantially twice the spacing between adjacent ceiling support members of said first set,

and wherein said diffusers have a length substantially equal to the spacing between adjacent ceiling sup port members of said first set.

11. The apparatus of claim 9 wherein the ceiling support members of said first set are equally spaced,

and wherein said diffusers have a length substantially equal to the spacing between adjacent ceiling support members of said first set.

12. The apparatus of claim 7 wherein said linear plenum members are polygonal in transverse cross section and are relieved at the fold lines thereof to accommodate the formation of the comers of said polygon shape,

and said pans include means for engagement with said linear plenum members to connect said linear plenum members to said pans and hold said linear plenum members in said polygon shape.

13. The apparatus of claim 7 wherein said pans include flanges along the longitudinal sides of said pan projecting from the basic plane of said pans,

wherein means is provided along the longitudinal edges of each of said openings to provide flanges projecting from said basic plane in the same direction as said longitudinal side pan flanges,

and wherein said linear plenum member wall portions include portions extending along said pans and engaged between said longitudinal side pan flanges and said opening flanges to hold said linear plenum members on said pan.

14. The apparatus of claim 1 including a plurality of generally planar extractor blades,

and means connecting said extractor blades in said opening at an angle to said pan and for independent pivotal movement about an axis generally parallel to said pan.

15. In combination with a generally planar suspended ceiling means defining an elongated slot in said ceiling,

first and second generally elongated pans each having a pan surface terminating in marginal ends and sides, said first and second pans arranged end-toend and with said pan surface spaced above said means defining said slot,

means including wall portions defining a generally elongated air plenum chamber,

' means defining an opening in each of said pans with the opening in one of said pans being spaced from the opening in the other of said pans,

said pan surfaces being closed except for said openings,

means connecting said plenum chamber to said pans with a part of the wall portions thereof engaged with said pans and with said air plenum chamber having open communication with said openings.

means for delivering air to said air plenum chamber for discharge through said openings,

and passage means extending between said openings and the portions of said slots underlying said openings and defining a passage for directing air passing through said openings to and for discharge through said portions of said slot underlying said openings,

the portions of said slot adjacent the portions of said slots through which air is discharged underlying said closed portions of said pans so that air may return therethrough into the area above said sus-

Claims

1. In combination in a suspended ceiling including a plurality of ceiling members, a plurality of ceiling support members, and means defining an elongated, linear slot in said ceiling, the improvement of an air delivery arrangement comprising, in combination, means defining a generally elongated, linear pan having marginal ends and longitudinal sides, means defining an elongated opening in said pan having an extension generally parallel to the longitudinal axis of said pan, the length of said opening being less than the length of said pan and said pan being otherwise closed, means defining a generally elongated, linear plenum member having wall portions defining a plenum chamber, means connecting said linear plenum member to said pan with said plenum chamber having open communication with said opening and with a portion of said wall portions engaged with a portion of said pan, means for delivering air to said plenum chamber for discharge through said opening, means at said opening for connection to the means defining said slot along only a limited length of said slot corresponding generally to the length of said opening so that air will be discharged through said slot only through said limited length, and said pan being spaced from said ceiling support members so that air delivered to said plenum chamber passes through said opening for discharge through said slot while the length of said slot adjacent that through which air is discharged underlies a closed extension of said pan and provides an air return.

2. The apparatus of claim 1 wherein said means connected at said opening comprises a diffuser assembly including, spaced walls projecting laterally relative to said pan and defining a passage therebetween, and pattern control means in said passage to deflect air flowing through said passage prior to discharge through said slot.

4. The apparatus of claim 1 wherein said pan includes means for engagement with said linear plenum member to connect said linear plenum member to said pan, and wherein said opening is spaced inwardly from the longitudinal sides of said pan.

5. The apparatus of claim 1 wherein said linear plenum member is polygonal in transverse cross-section and is relieved at the fold lines thereof to accommodate the formation of the corners of said polygon shape, and said pan including means for engagement with said linear member to connect said linear plenum member to said pan and hold said linear plenum member in said polygon shape.

6. The apparatus of claim 5 wherein said pan includes flanges along the longitudinal sides of said pan projecting from the basic plane of said pan, wherein means is provided along the longitudinal edges of said opening to provide flanges projecting from said basic plane in the same direction as said flanges along the longitudinal sides of said pan, and wherein said linear plenum member wall portions include portions extending along said pan and engaged between said longitudinal side pan flanges and said opening flanges to hold said linear plenum member on said pan.

7. The combination of claim 1 wherein said ceiling support members comprise a first set of mutually parallel ceiling support members and a second set of mutually parallel ceiling support members arranged generally perpendicular to said first set, including a plurality of said pans arranged end-to-end and all generally identical in construction and each having a length greater than the spacing between adjacent ones of said first set of ceiling support members, including a plurality of said linear plenum members connected end-to-end parallel to said second set of ceiling support members, and wherein at least two of said pans include said opening and said means connected at said opening, one opening and the means connected thereto spaced from the other opening and the means connected to it, so that air delivered to said plenum chamber passes through said openings for discharge through longitudinally spaced portions of said slot while the lengths of said slot adjacent those longitudinally spaced slot portions through which air is discharged underlie closed extensions of said pans and provide air returns.

8. The apparatus of claim 7 wherein said means connected at said openings comprise diffuser assemblies including spaced walls projecting laterally relative to said pans and defining a passage therebetween, and pattern control means in said passage to deflect air flowing through said passage prior to discharge through said slot.

9. The apparatus of claim 7 wherein said means connected at said openings each comprise a collar having spaced side and end walls projecting laterally relative to said pans to define a passage therebetween through which air from said plenum chamber passes for discharge through said slot.

10. The apparatus of claim 8 wherein the ceiling support members of said first set are equally spaced, wherein said pans each have a length substantially twice the spacing between adjacent ceiling support members of said first set, and wherein said diffusers have a length substantially equal to the spacing between adjacent ceiling support members of said first set.

11. The apparatus of claim 9 wherein the ceiling support members of said first set are equally spaced, wherein said pans each have a length substantially twice the spacing between adjacent ceiling support members of said first set, and wherein said diffusers have a length substantially equal to the spacing between adjacent ceiling support members of said first set.

12. The apparatus of claim 7 wherein said linear plenum members are polygonal in transverse cross section and are relieved at the fold lines thereof to accommodate the formation of the corners of said polygon shape, and said pans include means for engagement with said linear plenum members to connect said linear plenum members to said pans and hold said linear plenum members in said polygon shape.

13. The apparatus of claim 7 wherein said pans include flanges along the longitudinal sides of said pan projecting from the basic plane of said pans, wherein means is provided along the longitudinal edges of each of said openings to proVide flanges projecting from said basic plane in the same direction as said longitudinal side pan flanges, and wherein said linear plenum member wall portions include portions extending along said pans and engaged between said longitudinal side pan flanges and said opening flanges to hold said linear plenum members on said pan.

14. The apparatus of claim 1 including a plurality of generally planar extractor blades, and means connecting said extractor blades in said opening at an angle to said pan and for independent pivotal movement about an axis generally parallel to said pan.

15. In combination with a generally planar suspended ceiling means defining an elongated slot in said ceiling, first and second generally elongated pans each having a pan surface terminating in marginal ends and sides, said first and second pans arranged end-to-end and with said pan surface spaced above said means defining said slot, means including wall portions defining a generally elongated air plenum chamber, means defining an opening in each of said pans with the opening in one of said pans being spaced from the opening in the other of said pans, said pan surfaces being closed except for said openings, means connecting said plenum chamber to said pans with a part of the wall portions thereof engaged with said pans and with said air plenum chamber having open communication with said openings, means for delivering air to said air plenum chamber for discharge through said openings, and passage means extending between said openings and the portions of said slots underlying said openings and defining a passage for directing air passing through said openings to and for discharge through said portions of said slot underlying said openings, the portions of said slot adjacent the portions of said slots through which air is discharged underlying said closed portions of said pans so that air may return therethrough into the area above said suspended ceiling.