Patent Publication Number: US-2010112929-A1

Title: Recessed fan inlet cover

Description:
TECHNICAL FIELD 
     The invention relates to a recessed sound attenuating fan inlet cover with a flush outer surface profile. 
     BACKGROUND OF THE ART 
     Exhaust fans are well known in the prior art, for example fans which are installed in ceilings of residential or commercial buildings to exhaust air from kitchens or bathrooms. In general, a sheet metal fan enclosure houses a rotating blower wheel or fan driven by an electric motor. The enclosure has an inlet opening to intake air into the fan which is then expelled from the enclosure through an outlet into an exhaust duct. 
     For visual effect, dust control, noise control and to define an inlet airflow path, fan enclosures are usually fitted with a cover which can range from a simple grill or grate to relatively complex covers which attempt to produce less turbulent airflow and reduce propagation of sound from the electric motor and fan blade themselves. Conventional enclosures are usually of minimum size to house the fan and motor. Conventionally, the covers extend over the fan enclosure opening and extend outwardly past a surface of the wall or ceiling into which they are mounted. Conventional covers intake air laterally reducing the perception of airflow turbulence directly below or in front of a fan cover. 
     It is desirable to provide a fan enclosure cover that provides less turbulent airflow reducing noise generated by airflow and friction, that reduces propagation of vibrations and sound from the electric motor and fan blades, that is aesthetically pleasing and that reduces the visual impact of the fan cover as much possible. 
     Features that distinguish the present invention from the background art will be apparent from review of the disclosure, drawings and description of the invention presented below. 
     DISCLOSURE OF THE INVENTION 
     The invention provides a recessed fan inlet cover, for covering an enclosure inlet opening of an exhaust fan enclosure to provide an air flow channel into the fan enclosure while impeding sound emission from the fan enclosure, the fan inlet cover comprising: a cover frame having an outer peripheral edge extending outward of the enclosure inlet opening and having an inner edge defining a substantially planar frame surface, the frame having an upwardly recessed mounting surface joined to the inner edge with an arcuate wall, the mounting surface having an intake opening; and a cover plug mounted to the recessed mounting surface downwardly spaced from the mounting surface, the plug having a substantially planar plug surface co-planar with said frame surface, the plug having an outer peripheral edge with an inwardly projecting lip, the plug having a sound absorbing layer on an upper surface opposite said planar plug surface; wherein an air flow channel is defined between said arcuate wall and said lip. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be readily understood, one embodiment of the invention is illustrated by way of example in the accompanying drawings. 
         FIG. 1  shows a vertical section through a conventional prior art fan enclosure having a cover plate extending downwardly beyond a ceiling surface and drawing air into the inlet of the fan or blower to be expelled through the enclosure outlet and lateral exhaust duct. 
         FIG. 2  shows a bottom perspective view of a recessed fan inlet cover according to the invention. 
         FIG. 3  shows a plan view of the inlet cover according to the invention. 
         FIG. 4  shows a side view of the recessed fan inlet cover. 
         FIG. 5  shows a perspective view similar to  FIG. 2  with the cover plug removed to show the cover frame by itself. 
         FIG. 6  is a sectional view through the recessed fan inlet cover and through the exhaust enclosure. 
         FIG. 7  shows a sectional view similar to  FIG. 4  illustrating the arcuate wall surface of the cover frame and the opposing inwardly projecting lip of the plug which defines the airflow channel into the fan enclosure. 
     
    
    
     Further details of the invention and its advantages will be apparent from the detailed description included below. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a vertical sectional view through a prior art exhaust fan enclosure  1 . The exhaust fan enclosure  1  is mounted to the ceiling  2  in a conventional manner known to those skilled in the art. The enclosure  1  is generally of sheet metal having a inlet opening  3  covered by a fan inlet cover  4 . An electric motor  5  drives a rotating fan or blower  6  to intake air as indicated with arrows in  FIG. 1  from a central intake and outlet duct  7  from the enclosure. The electric motor  5  and air turbulence caused by the blower  6  creates sound which can be propagated downwardly into the room from which the air is exhausted. The function of the fan inlet cover  4  is to direct airflow into the central blower inlet, to visually disguise the opening  3  to the fan enclosure  1  and to reduce the noise propagated into the room from the motor  5  and fan  6 . 
     As indicated in  FIG. 1 , typically the cover  4  extends downwardly from the ceiling  2  into the room by dimension “d”. Designers may assume that extending the cover  4  into the room is necessary to draw in air laterally from a large area. However, extending into the room by dimension “d” disturbs the otherwise flush surface of a ceiling or wall and disturb the aesthetic appeal of a room. For example, in a well appointed washroom, the inexpensive plastic fan cover is generally the least expensive and least attractive element in the room, compared to light fixtures, plumbing fixtures, tiles, mirrors, and linens. However, to exhaust air, some type of fan cover is required. 
     In contrast, the present invention discloses in  FIGS. 2-7  a novel recessed fan inlet cover  8  that is also positioned over the enclosure inlet opening  3  of an exhaust fan enclosure  1 . The fan inlet cover  8  is recessed to provide a flush surface substantially planar across the surface of the cover  8 . 
     As seen in  FIG. 6 , the recessed cover  8  has a central portion which is recessed into the enclosure inlet opening  3  to define a novel means of providing an air inflow channel  22  to reduce turbulence as well as to mount sound absorbing material in a central plug  17  of the cover  8  as described below. 
     Further, a substantially planar lower surface  18  of the plug  17  and frame  9  of the cover  8  intrudes minimally into the room below the ceiling  2  surface from which air is exhausted. 
       FIGS. 2 ,  3 , and  4  show the outer surfaces of a recessed fan inlet cover  8  for covering an enclosure inlet  3  of an exhaust fan enclosure  1  (see  FIG. 6 ). The recessed fan inlet cover  8  provides an airflow channel  22  into the fan enclosure  1  while impeding sound emission from the fan enclosure  1 . 
     As seen in  FIGS. 2 ,  3  and  4  the fan inlet cover  8  includes a cover frame  9  having an outer peripheral edge  10  that extends outward of the enclosure inlet opening  3 . The cover frame  9  has an inner edge  11  that together with the outer edge  10  defines a substantially planar frame surface  12  therebetween. 
     As seen in  FIGS. 5 ,  6  and  7 , the frame  9  has an upwardly recessed mounting surface  13  joined to the inner edge  11  with an arcuate wall  14 . The mounting surface  13  has an interior intake opening  15  through which air drawn from the room enters into the fan intake. A sloping planar wall  16  optionally extends upwardly and inwardly from the inner edge  11  to the arcuate wall  14 . 
     Referring to  FIGS. 2 ,  3  and  4 , the recessed fan inlet cover  8  has a centrally positioned cover plug  17  mounted to the recessed mounting surface  13  and downwardly spaced from the mounting surface  13  to define an airflow channel  22 . The plug  17  has a substantially planar plug surface  18  that is substantially co-planar with the frame surface  12 , best seen in  FIG. 4 . In this manner, the recessed fan inlet cover  8  intrudes a minimal amount into the ceiling area of the room from which air is exhausted. The recessing of the air channel  22  and cover plug  17  results in a minimal intrusion. 
     The cover plug  17  has an outer peripheral edge  19  for example seen in  FIG. 7  with an inwardly projecting lip  20 . To absorb and prevent propagation of sound from the electric motor  5  and fan blower  6 , the plug  17  includes a sound absorbing layer  21  on an upper surface opposite to the planar plug surface  18 . The airflow channel  22  therefore is defined between the arcuate wall  14  and the lip  20 . As best seen in  FIG. 7 , the lip  20  and sloping planar wall  16  can be in parallel orientation with smooth rounded edges  19  and smooth transition to the arcuate wall  14  to reduce airflow turbulence and smooth the intake of air flow. 
     Preferably, the airflow channel  22  has an overall intake area relative to the enclosure inlet opening area in the range of 40 to 60% and most preferably in the range of 45 to 55%. Utilizing the cover plug  17  spaced from the recessed portion of the cover frame  8  to define the airflow channel  22  enables a relatively large intake area for the airflow channel  22  with visual masking of the blower  6  as indicated by line of sight  23  in  FIG. 7 . The sound absorbing layer  21  combined with the orientation of the frame  9  and plug  17  prevents sound from escaping in a direct path thereby reducing the propagation of sound from the electric motor  5  and fan  6 . 
     The recessed space created between the plug  17  and frame  9 , the space created within the layer  21  and above the plug  17  can accommodate an electric night light, motion sensors, humidity sensors, smoke detectors and other wall/ceiling mounted devices. Since electric power and conductors must be provided to power and control the fan motor  5 , such areas of the cover  4  can conveniently house such other devices and connect to wiring without other ceiling openings, separate junction boxes and visual disturbance of the ceiling or wall. 
     Although the above description relates to a specific preferred embodiment as presently contemplated by the inventor, it will be understood that the invention in its broad aspect includes mechanical and functional equivalents of the elements described herein.