Abstract:
A sound-baffling arrangement for use in conjunction with an air-handling unit. One or more sound baffle columns are mounted for rolling or sliding movement within the interior of the air handling unit housing. Each baffle column may be selectively moved between a use position proximate to the fan assemblies, and a non-use position more distal from the fan assemblies. The movable sound baffles permit the air-handling unit to be fabricated to fit within a smaller housing, and thus to have a smaller, more economical footprint.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention (Technical Field) 
   The present invention relates to air handling units, such as which move large volumes of air with motor-driven fans, and relates particularly to sound-attenuation components for such units, and specifically to movable sound attenuating baffles for air handling units. 
   2. Background Art 
   Custom air handling units (AHU) are mechanical equipment that deliver tempered and/or filtered air (via ductwork) to a building or portions of its interior space.  FIGS. 5 and 7  of the drawing figures depict the general layout of an air handling unit conventional to the art. Because the one or more fans  20  contained within the AHU to move the air can be quite noisy, it is common to install a bank of passive sound-attenuating baffles  10  between the fan(s)  20  and the intake or discharge port (or both) of the AHU as needed. The baffles  10  may either be self-supporting members arranged parallel to each other, or an array of modules that, like a filter bank, fill the interior cross-section of the AHU&#39;s airflow-conveying tunnel. Each baffle  10  has a rectangular, flat-oval or teardrop-shaped chord profile of some thickness, and the baffles are positioned so that the spacing between them is a predetermined distance. The sound attenuating performance of these baffles  10  depends on this distance or “passage width”, the baffle thickness, the baffle length and its materials. 
   Typically, an individual baffle is composed of acoustically absorbing glass fiber batting fill, surrounded by a perimeter flow-facing skin of perforated metal that conforms to the desired chord profile and protects the fill. To separate the fill from the gas flow, without unduly impeding the transmission of sound from the flow into the acoustically absorbent media, an additional impermeable thin film sometimes is placed between the glass fiber and the perforated metal. Like filter banks, heat transfer coils, and other common components installed serially within the AHU air tunnel, these baffles or “sound traps” are—with respect to an AHU operating normally—permanent, immobile fixtures that occupy a fraction of the AHU&#39;s footprint. 
   In the marketplace for heating, ventilation and air-conditioning (HVAC) systems where such custom AHUs are engineered and sold, the size of an AHU&#39;s footprint can have a direct impact on its cost and likelihood of being selected. Hence, the smaller the footprint, the more competitive (from a commercial standpoint) a custom AHU becomes. 
   An AHU footprint is occupied by the physical lengths of the components and clearances reserved to enable access for component inspection, service and removal. For instance, one will usually find, at a minimum, a two-foot-long clear section upstream of a filter bank. This allows maintenance personnel to access individual filter modules and, if needed, replace dirty ones with clean modules. 
   In the case of sound traps positioned immediately downstream of a belt-driven fan  20 , it is customary to reserve approximately two feet (or more) of AHU length between the belt-drive assembly and the intake side of the sound trap including the baffles  10  ( FIG. 7 ) This permits convenient walking clearance around the fan-drive assembly  20 . On the downstream side of the sound traps, there is usually a clearance of two or more feet to allow efficient diffusion of airflow discharging from the passages between parallel baffle surfaces. Without this downstream clearance during AHU operation, the aerodynamic resistance of the sound traps (and that of serially adjacent airflow-conveying components) tends to increase. Thus, industry practice maintains this clearance downstream of sound traps within an AHU. 
   But because the downstream clearance only impacts AHU performance when it operates, such a clearance is not required when the AHU is off and undergoing inspection or maintenance. This space can be used alternatively, as described herein. 
   SUMMARY OF THE INVENTION 
   Movable baffle columns for use in conjunction with an air-handling unit. One or more baffle columns are mounted for rolling or sliding movement within the interior of the air handling unit housing. Each baffle column may be selectively moved between a use position proximate to a fan assembly, and a non-use position more distal from a fan assembly. The movable baffles permit the air-handling unit to be fabricated to fit within a smaller housing, and thus to have a smaller, more economical footprint. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated into and form a part of this specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating a preferred embodiment of the invention and are not to be construed as limiting the invention. In the drawings: 
       FIG. 1  is a perspective view of a column baffle according to the present disclosure, shown positioned horizontally (uninstalled) to show its bottom; 
       FIG. 2  is a perspective view of the bottom of the baffle column seen in  FIG. 1 , showing a pair of rollers; 
       FIG. 3  is a partial perspective view, from above, of a portion of an apparatus according to the present disclosure, showing the bottom front edges of four baffle columns, disposed upon correspond tracks secured to the floor of an air handling unit; 
       FIG. 4  is a partial perspective of the top front edges of three baffle columns, of a portion of an apparatus of this disclosure, showing the tops of the baffle columns slidably engaged with guide channels defined on the ceiling of an air handling unit housing; 
       FIG. 5  is a side sectional view, taken along line A-A in  FIG. 7 , of an air handling unit known in the art, depicting an immobile baffle column; 
       FIG. 6  is a is a side sectional view, taken along line B-B in  FIG. 8 , of an air handling unit according to the present disclosure, depicting a baffle column movable between a non-use maintenance position (shown by solid lines) and a use or operating position (shown in phantom lines); 
       FIG. 7  is a top plan view of an air handling unit known in the prior art, with a plurality of immobile baffle columns; and 
       FIG. 8  is a top plan view of an air handling unit according to the present disclosure, showing a plurality of baffle columns independently movable along associated floor tracks, shown by solid lines in a non-use position, their use position being depicted in phantom lines. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Best Modes for Carrying Out the Invention 
   The present disclosure is of an AHU apparatus having a reduced footprint without compromising AHU performance. By installing self-supporting sound-attenuating baffles on tracks, with complementary rollers or other means that permit translational movement, the presently disclosed apparatus permits the creation of temporary clearances that maintenance personnel need when an AHU is not operating. After maintenance completes its inspection and/or service, the baffles are returned to original, functional, positions prior to re-actuating the AHU. 
   A conventional wisdom that may have prevented the apparatus of the present disclosure from appearing in known AHU systems is that access sections between AHU components are considered to doubly function as regions where airflow can mix, concentrate or diffuse as the design intends. But these airflow considerations are relevant only when the AHU is in operation; so, the present apparatus exploits the fact that internal component layout can be more compact or otherwise assume a different configuration when the AHU is turned off (for maintenance or the like). 
   Attention is invited to  FIGS. 1 and 2 , which depict the bottom of a baffle column  10  according to this disclosure. The baffle column  10  may be a closed plenum assembled from metal sheets. The bottom of each column is provided with at least two rollers  12 ,  12 ′. In the depicted embodiment, the two rollers  12 ,  12 ′ are rotatably mounted near the front and rear edges of the column  10  respectively. Each roller preferably may be fabricated from a rigid durable plastic, although rollers made from metal alloy or other materials may be suitable. Each roller has lubricated or ball-bearing contact with its axle, so that the roller freely rotates about a horizontal axis when the baffle column  10  is vertically oriented for use. In the embodiment depicted, each roller has a circumferential groove (i.e., the roller is configured like a pulley wheel) which is engageable with a floor track upon which the baffle column rolls. 
     FIGS. 3 and 4  show four baffle columns  10  installed for use. The columns are disposed vertically. As seen in  FIG. 3 , longitudinal tracks  14  are secured to the interior floor panel of the AHU, and serve to guide the movement of the baffle columns  10 . A track  14  has a convex (e.g. a peaked inverted “V”) profile complementary to the concave profile of the peripheries of the rollers, so that the rollers engage the tracks and roll along them. The engagement of the rollers with a track prevents the baffle column from moving in any direction except parallel to the track. Thus, each baffle column can roll to and fro within an imaginary vertical plane containing the corresponding track. The number of tracks corresponds to the number of baffle columns to be deployed, and the tracks ordinarily are disposed mutually parallel, so that adjacent baffle columns move in parallel planes. Further, each track  14  is longer than the length of its associated column. The extra length of a track  14 , relative to its column  10 , is approximately equal to the distance the baffle column rollably translates between its “use” and “non-use” positions. 
   It will be apparent to one skilled in the art that instead of convexly configured tracks and complementary concavely configured rollers, the apparatus may feature rollers having convex peripheries, engageable into concave groove-tracks defined on or in the floor. 
     FIG. 4  shows the tops of three baffle columns installed for use. The ceiling panel of the AHU is provided with parallel channels  17  of any suitable construction, to support and guide the top of each baffle column  10 . In the depicted embodiment, the channels  17  are fashioned from metal flanges secured to the AHU ceiling; pairs of flanges are spaced apart a distance corresponding to the lateral thickness of the top of a baffle column. The channels  17  maintain the tops portions of the baffle columns  10  in parallel and properly spaced relation, and hold the columns against any lateral shifting. Each channel preferably has a smooth, flush, contact with both sides of the column; contact between channel and column is a sliding contact, aided by suitable lubrication as needed. 
   Each channel  17  is longer than the length of its associated column  10 . The extra length of the channel  17 , relative to its baffle  10 , is approximately equal to the distance the baffle column rollably translates between its “use” and “non-use” positions. 
   It will be apparent to one skilled in the art that instead of concave configured channels in the ceiling which receive the tops of the baffle columns  10 , the apparatus may feature convex ceiling tracks that engage into grooves along the tops of the baffle columns. 
   Continued reference to  FIG. 4  shows how the front edge and the rear edge of each column  10  are provided each at its top with a sliding pin latch  16 . Each pin latch  16  is selectively slidable up and down (along a generally vertical line), so to engage or disengage with a corresponding latch socket  18  in the ceiling of the AHU. In the depicted embodiment, the latch socket  18  is defined in the channel, as by the simple expedient of attaching a metal loop onto the short flange defining the end of the ceiling channel  17 . Other suitable socket means are apparent and may be used. The latch pins  16  are used to releasably lock the baffle column  10  in position at either extreme of its travel along the tracks  14  (that is, at either the “front” end or the “back” end of the tracks and channels). Thus, each baffle column  10  can be releasably locked in its “use” position or in its “non-use” position by sliding the latch pin  16  into the appropriate latch socket  18 . Of course, other means for releasably locking a baffle column in use or non-use position may be used. 
   Thus, the depicted embodiment utilizes eyelet bolts or similar hardware to manually temporarily fix each column  10  to any of one, two (or more, such as incremental) specific positions along the track  14 . Other embodiments might employ motors or actuators to enable individual or multiple baffle translation and position fix (or even lock) via some form of remote control. For instance, a maintenance worker might activate a switch on a box outside the AHU that tells these actuators to move the columns  10  to the non-use “access” position instead of the “use” or “operating” position, and to lock them position. 
   From a visual comparison of the two plan views of a sample AHU in  FIGS. 7 and 8 , this method ( FIG. 8 ) of baffle installation is superior to fixed and immobile installations of prior art ( FIG. 7 ), in that it creates an opportunity for reducing or even eliminating what would otherwise be a typical access section. The benefit results from the decreased overall AHU footprint, which should reduce fabrication cost when compared to a functionally equivalent but slightly longer AHU with the conventional layout of components and associated clearances or access sections. 
   As explained, the means of providing this translational movement described in this embodiment employ v-grooved casters  12  on the top and bottom ends of each baffle  10 . These casters  12  ride an angle-shaped track  14  for smooth movement. Surrounding the possible pathways that the baffle ends travel is a short solid metal barrier, which helps reduce the opportunity for gas flow, and the fan sound it conveys, to bypass the intended passages between the parallel baffles. While the baffles are often identical in chord profile and parallel with respect to one another, the chord profile of each could be different from its neighbor, and the actual passage bounded by baffle surfaces and “seen” by the traversing gas flow could be non-parallel (e.g., the adjacent baffle surfaces form a gradually diffusing evase shape described by some included angle). 
   Referring to  FIGS. 5 and 7 , it is seen that the baffle columns  10  of a conventional AHU are fixed in location in relation to the other components of the AHU, including the fan assemblies  20  and a downstream feature such as a directional plenum  22  or a filter bank or the like. In known AHU configurations, the columns are stationary with a space of, say, twenty-six inches between the front or leading edges of the columns  10  and the rearmost portions of the fan assemblies  20 . Similarly, access demands that there be a space of, for example, at least ten inches between the rear edges of the columns and the front of the downstream element  22 . 
     FIGS. 6 and 8 , however, illustrate that the baffle columns  10  of the present apparatus selectively moveable between a non-use or maintenance position and a “use” or operating position. In  FIGS. 6 and 8 , the baffles  10  in the maintenance position are shown in solid lines, while phantom lines show them in the use or operation position. In the operation position (phantom lines), the baffle columns  10  are temporarily but securely situated with their front or leading edges substantially proximate to the fan assemblies  20 , with little space (e.g., six to twelve inches) separating the baffles  10  from the fan assemblies  20 . However, when the necessity to access AHU interior components arises, the latch mechanisms  16 , 18  holding the baffles  10  in the operating position are disengaged or released; each baffle column  10  can then be rolled or slipped rearward along its respective track  14 , toward the downstream end of the AHU (e.g., toward the discharge plenum  22 ). Such translational shifting may be continued until a baffle  10  obtains its rearward-most position along its respective track  14 , and thus is in the non-use maintenance position (as depicted by the solid-line baffles in the drawing figures). In the maintenance position, each baffle  10  is spaced a distance of, for example, 30 inches from the fan assemblies  20 . Each baffle column that has been relocated to its maintenance position can be reliably locked into that position by engaging lock latches  16 ,  18  as described previously herein; 
   As seen in  FIGS. 6 and 8 , after all the baffles have been moved to their maintenance positions, there is provided ample access space between the front edges of the baffles and the rear portions of the fan assemblies. In the non-use maintenance position, the baffles  10  extend into, or overlap with, or extend over, a downstream element  22 ; however, such positioning does not interfere with the function of the AHU, since the baffle columns are returned to their operating positions before the AHU is restored to service and actuated. When releasably locked in their operating positions (again, as represented by the phantom lines in the figures), the baffles  10  are spaced forward from the downstream plenum or other element  22  an adequate distance to permit service personnel to pass safely between the baffles and the downstream element  22  as needed. Access doors  36 ,  36 ′ may be provided in the AHU housing to permit personnel access to the AHU interior, as needed, but then closed when the AHU is in operation. A forward door  36 ′ offers ready access to the upstream or intake plenum  38  to the fan assemblies  20  ( FIG. 8 ). 
   It is immediately understood that as a result of having longitudinally movable baffle columns  10  that can be selectively shifted between maintenance and operating positions, the overall footprint length of the AHU can be shortened. A comparison of  FIGS. 7 and 8  shows that the length of the AHU can be shortened, in this disclosed embodiment, by a distance (e.g., twenty-four inches) approximating the distance of to-and-fro movement of the columns  10 . 
   Although the afore-described apparatus relates to a sound trap bank, it likewise could relate to a filter bank or some other AHU component that could be moved with the AHU otherwise intact and the fans inoperative. For example, filter banks could be another application for this means of translational movement: in general, filters are even lighter (in weight) than sound attenuating baffles. Heat transfer coils, in contrast, likely could not take ready advantage of the benefits of this apparatus, since their positions are fixed by piping connections to the building where the AHU is installed. 
   It is known for AHU components to be fabricated and/or installed so that they are removable with some level of mechanical effort. Even a heat transfer coil bank may feature piping connections and a rack that allows it slide laterally into or out of an AHU. But in the present apparatus and methodology, certain lightweight components, namely a sound trap, or possibly a filter or other components that do not require fixed positions when the AHU is inoperative (or do not have inflexible physical or electrical connections to systems external to the AHU), can resemble a movable shelf—whether such movement is manual or motorized—and yield similar space savings that enable a smaller AHU footprint and hence competitiveness. 
   Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all applications, patents, and publications cited above are hereby incorporated by reference.