Ducted/ductless range hood

A range hood for an enclosure, which may be either ducted or ductless, comprises a hood having an inner compartment, said inner compartment having an air inlet aperture and first and second air outlet apertures; a blower means disposed within said hood and adapted to draw air from said enclosure through said air inlet aperture into said inner compartment and to discharge the air from said inner compartment through said outlet apertures; a damper member mounted for movement between a first position blocking said first outlet aperture, sand a second position not blocking said first outlet aperture, said damper member being normally biased to said first, blocking position; a first means for selectively locking or unlocking said damper member in said first position; and a second means for selectively opening or closing said second outlet aperture, such that, when said second outlet aperture is open and said damper member is locked in said first position, the air drawn into said inner compartment by said blower means is discharged therefrom through said second outlet aperture and, when said second outlet aperture is closed and said damper member is not locked in said first position, the air drawn into said inner compartment by said blower means moves said damper member to said second position and is discharged out of said first outlet aperture.

FIELD OF THE INVENTION 
The invention relates to a range hood unit which is provided with means 
whereby the direction of the air flow in the hood is readily controlled; 
the hood being easily changeable into either a ducted unit--exhausting air 
outside the ventilated enclosure--or a ductless unit--recirculating air 
inside ventilated enclosure. This conversion is accomplished without the 
necessity for revamping and reinstalling the range hood. 
RELATED ART 
The term range hood as used in this application means a box-like 
ventilating shield (open at the bottom), usually fabricated from sheet 
steel, which is designed to be installed in a horizontal position, spaced 
above a cooking stove or cooktop, for the purpose of removing the heated 
air, water vapor or steam, smoke particles, grease particles and volatile 
fat vapors, as well as the odors that result from many food cooking 
operations. The range hood can also remove from an enclosure stale air not 
associated with cooking. 
An essential component of any range hood is a fan or blower, powered by an 
electric motor, which provides an induced draft of air movement to draw 
the heated air and other volatile products of the cooking operation from 
the space above the burners into the hood. This removal of the heated air 
and other volatiles prevents their accumulation in the stove area and 
thereby results in cooler comfort conditions for the cook. The blower 
motor is usually controlled by a manually operated off-and-on switch. It 
can have various control positions, such as one "on" position, a low and 
high speed "on" position, low, medium, and high "on" positions, or a 
continuously variable speed control, as, e.g., a solid state type control. 
In the past, two basic types of range hoods have been utilized for home 
kitchens: ducted and ductless. The ducted hood is provided with an outlet 
orifice on the discharge side of the blower which is connected to a duct 
that discharges the heated air and other volatile and airborne products 
that are carried in the air stream to the air outside the kitchen. When 
the cooking range is in a kitchen location that does not afford convenient 
access to a wall in which a duct to discharge the heated air outside the 
building may be installed, the ductless type of range hood can be used. 
With the ductless hood the heated air from the cooking operation is first 
thoroughly filtered to remove grease, smoke and fine food particles and to 
absorb cooking odors, and is then returned to the room through a vent at 
the top of the hood, overhead and away from the cooking area. 
A major disadvantage of the ductless range hood as compared with a ducted 
hood is that the heated air and steam from food cooking are not removed 
from the kitchen, and consequently the cooling effect provided by the 
ducted hood is not obtained. However, this very property of the ductless 
range hood of delivering heat back to the ventilated enclosure results in 
a conservation of energy, which can be most advantageous in these times of 
diminishing and ever more costly energy resources. 
It has long been recognized that it would be beneficial to be able to use 
the heat from cooking ranges for heating the room in which the range is 
located. And it has further been realized that it would be desirable to 
provide a range hood which may be either ducted or ductless. One such hood 
is described in U.S. Pat. No. 3,690,245. To provide for a ducted operation 
utilizing this hood, a knock-out panel provided in the unit must be 
manually removed and the duct work must then be attached thereto. This 
type of unit suffers from the obvious drawback that once it is installed, 
the user cannot then select a different mode of venting of the heated air 
without a major alteration of the system. Consequently, the user loses the 
advantage of selectively directing the heated air where it could be most 
beneficial. For example, in winter it would be desirable to permit the 
heated air to circulate back to the area being vented for added warmth. On 
the other hand, in summer one would want to dispose of the heated air by 
venting it to the outside to keep the interior as cool as possible. 
Various attempts have been made to provide a venting system which can be 
converted from a ducted to a ductless mode of operation and vice versa 
with a minimum of effort. Although these attempts have met with a measure 
of success, the resulting ventilating systems often suffer from 
disadvantages such as an undue complexity in design and/or equipment, 
inefficiencies in operation, lack of versatility, etc. In U.S. Pat. No. 
2,634,718, for example, there is described a gas oven ventilating system 
wherein a flap valve is manually adjustable between two positions, so as 
to vent heated air either inside or outside the enclosure where the gas 
range is located. The venting arrangement disclosed in this reference is 
built into the gas range. This means that the user of the range is 
committed to this particular type of venting system, which would not be 
the case if the venting means were separate from the range. Also, it is 
desirable to have a venting system separate from the cooking appliance 
which can then be better utilized under more exhaust conditions than the 
one which is specifically tailored to a particular appliance. Another 
disadvantageous feature of the ventilating unit in U.S. Pat. No. 2,634,718 
is that it pulls the heated air being exhausted downward and thus loses 
the advantage in permitting the heated air to rise in the venting process. 
It is also known to use combinations of dampers for directing heated air 
either back into or out of the kitchen area. Such systems are described, 
for example, in U.S. Pat. Nos. 2,886,124 and 4,120,290. These venting 
arrangements generally require a number of working parts which must all 
cooperatively function to bring about the desired venting effect. The use 
of single dampers is also disclosed in U.S. Pat. No 4,120,290 but even 
these venting modes involve the interaction of a number of elements. 
An optional discharge venting system with a single damper is again 
described in U.S. Pat. No. 4,114,589. This system is built into an oven 
appliance and is limited to interior or exterior venting of the heated air 
from a food-processing oven or the like cooking appliance. Its range of 
operation is thus restricted and does not include, for example, the 
exhaustion of stale air from the room area where it's located. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide an improved ventilation 
unit having a simple and versatile design which can function as either a 
ducted or ductless unit. 
It is a further object of the present invention to provide a range hood 
unit having a relatively simple construction which can be easily converted 
from a ducted to a ductless mode of operation and vice versa without 
revamping and reinstalling the range hood. 
It is yet another object of the present invention to provide a range hood 
unit which can be readily adapted to either withdraw the heat from a 
cooking range and thus cool the ventilated enclosure or return the heat 
back to the enclosure and thereby effect a conservation of the heat 
energy. 
It is still another object of the present invention to provide a simple 
method for venting air to either the inside or outside of a ventilated 
enclosure, which can be utilized in various existing ventilation units 
without this dual capability, after suitable modification thereof. 
These and other objects of the invention will become more apparent as the 
description thereof proceeds. 
SUMMARY OF THE INVENTION 
The above objects were achieved in the ventilation system of the invention 
which has means for so controlling the direction of the air flow 
therethrough that the hood can be readily interconverted between ducted 
and ductless modes of operation. The range hood is suitably placed over 
the area to be exhausted so that the heated air and other volatile 
products of the cooking operation can flow into it. The hood is provided 
with a blower means which can take in the air and other volatiles from the 
enclosure being exhausted and blow them to the interior of the hood. 
Preferably, filtering means are placed between the vented enclosure and 
the blower means for air purification. The range hood of the invention 
further has control means for directing the air flow blown by the blower 
means either back into the enclosure being vented or outside said 
enclosure, said control means comprising means for confining said air flow 
to a passage back into said enclosure and for permitting said air flow to 
force its way out of said enclosure. 
The invention, more particularly, resides in a range hood for an enclosure 
comprising: 
(a) a hood including an inner compartment, said compartment having an air 
inlet aperture and first and second air outlet apertures; 
(b) a blower means disposed within said hood and adapted to draw air from 
said enclosure through said air inlet aperture into said inner compartment 
and to discharge the air from said inner compartment through said outlet 
apertures; 
(c) a damper member mounted for movement between a first position blocking 
said first outlet aperture and a second position not blocking said first 
outlet aperture, said damper member being normally biased to said first, 
blocking position; 
(d) a first means for selectively locking or unlocking said damper member 
in said first position; and 
(e) a second means independent of said damper member for selectively 
opening or closing said second outlet aperture, 
such that, when said second outlet aperture is open and said damper member 
is locked in said first position, the air drawn into said inner 
compartment by said blower means is discharged therefrom through said 
second outlet aperture and, when said second outlet aperture is closed and 
said damper member is not locked in said first position, the air drawn 
into said inner compartment by said blower means moves said damper member 
to said second position and is discharged out of said first outlet 
aperture.

DETAILED DESCRIPTION OF THE INVENTION 
This invention will be described as embodied in a range hood unit, either 
ducted or ductless, optionally having a filtering system, and constructed 
with the arrangement of the parts as illustrated in FIGS. 1-3. It is to be 
understood, however, that the dimensions, arrangement and assembly of the 
parts shown in this typical example could be changed in various ways, or 
the range hood could have multiple filters, and the concept of the 
invention would still be effective in permitting a range hood to 
interchangeably function in either a ducted or ductless operating mode. 
Referring now to the drawings and particularly to FIGS. 1-3, the range hood 
is shown as comprising a generally box-like structure open at the bottom, 
having top panels 10a and 10b, front panels 11a and 11b, and side panels 
12a and 12b (FIG. 1), and a back panel 13 (FIGS. 2 and 3). The panels on 
the other side of the range hood, corresponding to panels 12a and 12b, are 
not shown in FIG. 1. The range hood is suitably dimensioned for 
installation above a kitchen range and has keyhole slots 14 for mounting 
to an overhang, such as the bottom of a kitchen cabinet. 
On front panel 11a are provided louvers 15, an on-off light switch 16, and 
a fan speed control switch 17. In the exploded view of the range hood 
illustrated in FIG. 1, a cover panel 18 is shown somewhat removed from a 
position on front panel 11a, where it is operable to cover louvers 15. The 
side of cover panel 18 which is exposed to view can appropriately have a 
decorative design thereon. When cover panel 18 is not being used to block 
the openings provided by louvers 15, it may be placed on front panel 10b 
below the louvers or in a suitable storage area. Cover panel 18 is 
provided with a magnetic backing for attachment to panels 10b or 11a. It 
is, of course, obvious that cover panel 18 can be affixed to the hood by 
other fastening means. 
As can be seen in FIGS. 2 and 3, a fan 19 driven by an electric motor 20 is 
located in an inner compartment 21 within the hood below top panel 10a. 
Inner compartment 21 is bounded at the front by panel 11a, at the top by 
panel 10a, at the back by panel 13, at the bottom by panel 22, and at the 
sides by panels 23 (illustrated by broken lines in FIG. 1). A light or 
lights (not shown in the drawings) can conveniently be located within the 
hood, such as adjacent to side panel(s) 23. 
Inner compartment 21 has an inlet aperture 24, which is suitably circular 
in shape, in its bottom panel 22. Inlet aperture 24 provides the entry 
point for air drawn into inner compartment 21 by fan 19, which is located 
so as to effectively draw air from below the hood through said inlet 
aperture. Fan 19 and motor 20 can be held in place in the hood by any 
number of conventional means, such as by a bracket support. 
Two outlet apertures are provided for discharge of air from inner 
compartment 21, one for discharge to the exterior of the enclosure being 
ventilated and the other for discharge back to said enclosure. The numeral 
25 in FIG. 1 indicates the outlet aperture for discharge to the exterior 
of the ventilated enclosure. This opening is located above inner 
compartment 21 in top panel 10a. As illustrated in FIG. 1, it is suitably 
located toward the rear of panel 10a. The other outlet aperture for 
returning air to the ventilated enclosure is provided by louvers 15 
located in front panel 11a. 
Mounted above hood discharge opening 25 is an adapter assembly or housing 
26 to which is hingedly attached a damper 27. The adapter assembly and 
damper are formed of sheet metal or other suitable material. Damper 27 in 
the horizontal position illustrated in FIG. 1 serves to close outlet 
aperture 25 to the passage of air therethrough. The adapter assembly with 
damper is so constructed in accordance with the invention that the 
application of a locking means to the damper will operate to keep outlet 
aperture 25 closed and thus to prevent the passage of air through the 
aperture; and the release of the locking means will operate to permit the 
damper to be displaced through the force of air blown by fan 19 from the 
position in which it closes the outlet aperture and to thereby permit the 
air to pass through the outlet aperture. The damper assembly can be 
variously designed to accomplish this type of vent control. It should also 
be noted that the locking means for keeping the damper in the position 
closing the outlet aperture can be designed otherwise than described below 
and still fall within the scope of the present invention. For example, 
damper 27 can be locked closed by locking means applied directly or 
indirectly thereto. One such indirect locking means would be a blockage of 
the duct work between damper 27 and the exterior of the enclosure which 
would prevent air blown by fan 19 from moving damper 27 (described further 
below). 
Adapter assembly 26 is a four sided mounting (FIG. 1.) which can be secured 
to top panel 10a of the hood by any convenient means. The interior space 
bounded by the four sides of the adapter assembly provides a channel or 
opening for the passage of air therethrough. As illustrated in FIG. 1, 
adapter assembly 26 is provided with outwardly directed flanges from its 
side walls for attachment to panel 10a by means of screws. The front side 
of adapter assembly 26 curves forwardly from the top with its frontmost 
portion designed to rest on panel 10a and a small projection centrally 
located thereon for insertion into a raised slot (not shown) on panel 10a. 
Damper 27 is a rectangularly shaped plate (FIG. 4) and is formed of sheet 
metal or other suitable material. It is attached to adapter assembly 26 by 
means of hinges 28 provided in the back side of the adapter assembly, as 
shown in FIGS. 1-5. Support for damper 27 in its generally horizontal 
position closing outlet aperture 25 is provided by hinges 28 and by a 
small projection 29 attached to and extending rearwardly from the front 
side of adapter assembly 27 (See FIGS. 4 and 5). Projection 29 is located 
to the side of another projection 30 which is formed by bending down a 
small rectangular segment of the front side of adapter assembly 26. 
Projection 30 is centrally located on and also extends rearwardly from the 
front side of adapter assembly 26. It should be understood that other 
techniques can be employed in supporting damper 27 without departing from 
the scope of the present invention. 
Projection 29 is made of a relatively soft material, such as felt or other 
appropriate material, which can serve as a cushion on which damper 27 will 
rest in its position blocking outlet aperture 25. The upper surface of 
projection 29 is advantageously somewhat higher than that of projection 30 
so that projection 29 can serve in the manner of a bumper for preventing 
any bothersome noise from the damper's banging into projection 30. Damper 
27 has an area smaller than that of adapter assembly 26 so that it can 
move freely within the interior space defined by the adapter assembly. 
Transition section or duct 31 (FIG. 1) is made of sheet metal or other 
suitable material and is snugly mounted by any convenient means on adapter 
assembly 26. Duct 31 has four joined side walls and defines a generally 
rectangular channel extending upwardly from adapter assembly 26 to 
additional ducting 32, FIG. 1, which carries air discharged through outlet 
aperture 25 to the exterior of the household. As illustrated in FIG. 1 
cutouts are made at the four top corners of transition section 31 to 
facilitate mounting of the above duct section 32 thereon. The ducting 
above transition section 31 can be used to exhaust through the roof of the 
enclosure or through the wall (by using a right angle elbow above the 
transition section). It should be understood that the damper assembly and 
the duct section attached to it can be of a dimension and shape other than 
that shown and still fall within the scope of the present invention. It is 
also within the scope of the invention to have the transition section and 
the damper assembly combined into a single unit. 
A suitable locking means 33 (FIG. 1) is provided in transition section 31 
for selectively locking the damper plate in the position where it closes 
outlet aperture 25 or unlocking the damper plate and thereby permitting it 
to be forced upward by air blown by fan 19. Locking means 32 is centrally 
mounted on the front wall of transition section 31. The locking means 
includes control knob 34 mounted on a relatively short shaft 35 for 
rotation. The end of the rotatable shaft extends through an aperture 
provided in the front wall of transition section 31 (see FIGS. 4 and 5). A 
locking cam 36 (See FIG. 9) is attached to the part of shaft 35 extending 
through the wall of transition section 31 for rotation thereby. Locking 
cam 36 consists of a plate 38 having a small projection 39. A push-on clip 
37 (FIG. 5) serves to hold locking cam 36 on shaft 35 in a position such 
that portion 38 thereof abuts the interior side of the front wall of 
transition section 31 and portion 39 projects into the interior of the 
channel defined by the transition section. 
A raised portion 40 (FIG. 10) on the front face of knob 34 serves as an 
indicator of the position of locking cam 36 within transition section 31. 
With raised portion 40 of the knob in the horizontal position shown in 
FIG. 10 locking cam 36 is so fastened on shaft 35 that portion 38 thereof 
is in a vertical position with its finger 39 projecting therefrom backward 
and downward into the interior space of transition section 31. In this 
position projection 39 of the locking cam contacts damper 27 and functions 
to hold it in the generally horizontal position blocking outlet aperture 
25 shown in FIGS. 3, 5 and 6. Air blown by fan 19 is thereby prevented 
from passing through opening 25 and is instead recirculated through 
louvers 15 into the enclosure being ventilated, as described below. 
A clockwise 90.degree. rotation of knob 34 causes the shaft 35 and locking 
cam 36 to similarly rotate 90.degree. in the clockwise direction. Such a 
90.degree. rotation brings locking cam 36 to the horizontal position shown 
in FIGS. 7 and 8. In this position projection 39 no longer contacts or 
locks down damper 27, which therefore can swing freely on hinges 28 and be 
displaced upward by air blown by fan 19. A dimple 41 can be provided on 
the back interior side of the front wall of transition section 31 to aid 
in maintaining locking cam 36 in the horizontal, unlocking position, as 
shown in FIG. 7. As illustrated in FIG. 10, the front wall of transition 
section 31 can be provided with markings which indicate in which position 
of the control knob air can be recirculated inside the ventilated 
enclosure--raised portion 40 of knob in horizontal position--and in which 
position of the knob air can be exhausted outside the ventilated 
enclosure--raised portion 40 of knob in vertical position. 
Briefly, the operation of the venting system in accordance with the present 
invention can be described as follows: 
When it is desired to operate the range hood of the invention as a ducted 
unit (exhausting air outside the enclosure) knob 34 or other control 
device on transition section 31 is turned to move the locking cam 36 
within the transition section to the unlocking position. The position of 
locking cam 36 in the horizontal unlocking position, as seen from behind 
the front wall of transition section 31, is illustrated in FIG. 7. A side 
view of this portion is shown in FIG. 8. This allows the damper 27 to open 
and close freely. A decorative panel 18 or similar device is at the same 
time placed on the hood over the louvers 15 to cause the discharge of air 
blown by fan 19 to pass from the hood out through transition section 31 
and duct to the outside of the household. When locking cam 36 is in the 
unlocking position and fan 19 is turned off, damper 27 will naturally rest 
under the influence of gravity in the position blocking opening 25. In the 
ducted operation of the hood, the odor filter (described below) should be 
removed and stored for later use in the ductless operation. Such removal 
helps preserve the efficiency of the filter. The passage of air in the 
ducted operation of the range hood of the invention is shown by the arrows 
in FIG. 2. The opening of the damper plate would normally be desirable, 
for example, in the summer season when one might want heated air from the 
range to be discharged to the exterior of the household. 
On the other hand, in the winter season one might want to close the damper 
plate so as to add warmth to the household interior. In this case, the 
range hood is operated as a ductless unit (recirculating air inside the 
enclosure). This is accomplished by turning the selector knob 34 or other 
control device on the transition section 31 so that the locking cam 36 
within the transition section locks the damper 27 shut allowing no air to 
pass through the duct. The position of locking cam 36 in the vertical 
locking position, as seen from behind the front wall of transition section 
31, is illustrated in FIG. 6. A side view of this position is shown in 
FIG. 5. The decorative panel 18 or similar device covering the hood 
louvers 15 is at the same time removed to permit air blown by fan 19 to 
pass through the hood louvers and recirculate into the household. 
Additionally, an odor filter is suitably installed for the ductless 
operation. The passage of air in the ductless operation of the range hood 
of the invention is shown by arrows in FIG. 3. 
Another advantageous embodiment of the range hood of the present invention 
is illustrated in FIGS. 11-13. The range hood in this embodiment is 
similar in shape and design to the range hood of FIG. 1 previously 
discussed. It differs only in the locking and unlocking mechanism used to 
control damper 27. All other components of the range hood shown in FIGS. 
11-13 are the same as in the range hood of FIGS. 1-10. 
The locking and unlocking means for the range hood illustrated in FIG. 11 
comprises a manually operable closure member or control damper 42. Damper 
42 is a plate of sheet metal or other suitable material mounted in duct or 
transition section 31. The plate is rectangular in shape and has an area 
just slightly smaller than that of the rectangular opening provided in 
transition section 31 for air passage therethrough. The plate is received 
in duct section 31 as shown in FIGS. 11-13. Felt strips can suitably be 
located at its edges to prevent metal-to-metal contact between the 
interior surface of the transition section and damper 42 when the latter 
is in the horizontal position closing off the air passage through the 
duct. 
Damper plate 42 is attached by any convenient means to a rod 43 (FIG. 11) 
extending along the center thereof from one side wall of transition 
section 31 to the other. As illustrated in FIG. 11, one end of the rod is 
secured for rotation to one side wall of the transition section 31 and the 
other end extends through an aperture located in the other side wall of 
the transition section. The latter end is bent to provide a control handle 
44 which extends along the exterior surface of the side wall. 
The damper plate 42 is fixed or secured on a rode 43 and rotatable as an 
assembly therewith. Two dimples 45 are provided, one above the other, in 
the surface of the side wall of the transition section for holding handle 
44 in the horizontal position (See FIGS. 12 and 13). 
The ducted and ductless mode of operation of the range hood of FIG. 11 are 
illustrated in FIGS. 12 and 13, respectively. When it is desired to 
operate the range hood as ducted unit, cover panel 18 is installed over 
the louvers and control rod handle 44 is set in the vertical position 
shown in FIG. 12. Setting handle 44 in this position correspondingly sets 
damper 43 in the vertical position whereby it is in an unblocking relation 
with respect to the transition section. With this arrangement of cover 
panel 18 and damper 2, air blown by fan 19 forces damper 27 open and 
thereby passes to the exterior of the household, as illustrated by the 
arrows in FIG. 12. 
In the ductless mode of operation of the above embodiment of the range hood 
of the invention, cover panel 18 is removed from louvers and handle 44 is 
turned to the position between dimples 45. Damper 42 is thereby secured in 
the horizontal position illustrated in FIG. 13 with the result that it 
blocks off or closes the transition section to the passage of air. Thus 
air blown by fan 19 cannot lift damper 27 from its position closing outlet 
aperture 25 and must instead pass through louvers 15 to the interior of 
the household. 
Filtering means for use in the range hood of the invention are also 
illustrated in FIGS. 12 and 13. Although a ducted range hood could be 
operated without a filter, since the heated air, steam and other volatiles 
are discharged outside the building, such operation is unsatisfactory 
because grease and food particles tend to collect on the fan blades and in 
the discharge duct which then becomes unsanitary and also involves a fire 
hazard. The ducted hood therefore requires a grease filter for 
satisfactory, safe operation. The grease filter is an open-mesh, framed 
panel, installed within the range hood below the blower, as, e.g., in the 
position of unit 46 of FIG. 12. In this way all the heated air drawn into 
the hood by the fan first passes through the filter which collects 
virtually all of the grease and other food particles or spatter carried in 
the air stream. The grease filter is usually constructed from a 
non-corrodible metal, such as aluminum, usually in the form of coarse 
expanded mesh made from thin sheet aluminum. This expanded mesh is of open 
structure so as not to restrict appreciably the air flow induced by the 
fan. 
Also, it is preferably coated or chemically treated so as to increase its 
ability to adhere to and retain grease and other food particles in the air 
stream and to improve ease of cleaning the filter. An especially effective 
coating material for an aluminum mesh grease filter is "Teflon-S" (a 
polyfluorocarbon product of the DuPont Company), but various other 
synthetic grease-resistant coating materials may be used. Polymerized 
fluorocarbons, such as polytetrafluoroethylene and fluorinated 
ethylene-propylene, are the preferred coating compositions, due to their 
chemical inertness, resiliency, resistance to moisture and steam, wide 
range of service temperatures, heat resistance up to 500.degree. F. 
without carbonization, and resistance to embrittlement. 
Because substantial quantities of grease accumulate in the filter 
interstices from continued use of the range hood, the framed filter panel 
is installed so as to be easily removable for cleaning. The grease 
accumulation is easily removed by light agitation of the filter mesh with 
a detergent solution and the filter panel, after drying, may be 
re-installed in the hood for another period of service. 
A grease filter of the same kind as used in the ducted operation is also 
advantageous in the ductless operation of the range hood. Additionally, in 
the ductless mode of operation there is usually provided a granulated, 
activated charcoal filter to absorb cooking odors. An additional odor 
filter 47 is included in the filter arrangement shown in FIG. 13. In the 
ductless operation the range hood may also have a filter of spun glass 
fiber that may be chemically treated or coated to enable it to absorb 
smoke particles and also any fine grease particles that may not have been 
trapped by the aluminum mesh grease filter. The activated charcoal filter 
and the glass fiber filter are inexpensive and are intended to be replaced 
after a period of use, before they become clogged and ineffective. 
It is obvious that the concept of this invention is adaptable to 
prefabricated domestic range hood units of varying sizes and shapes, to 
provide them with a unique mechanism for controlling the direction of air 
discharge within the hood whereby it can be operated as either a ducted or 
ductless unit. The concept can, for example, be readily applied to the 
range hood unit described in U.S. Pat. No. 3,690,245. The invention 
therefore resides not only in the above-described range hood, but also in 
a method of venting air from an enclosure whereby the air is blown to the 
interior or exterior of the enclosure utilizing control means which either 
confine the air flow to a given path or permit it to force open an 
alternate path. 
Included within the scope of the present invention is a ductless/ducted 
hood conversion kit. The purpose of this energy saving kit is to permit 
conversion of a given existing range hood of appropriate design into one 
which is capable of either a ducted or ductless mode of operation. The kit 
comprises a cover panel 18, adapter assembly with damper 26 and damper 
control transition section 31, as illustrated in FIG. 1 of the drawings. 
The kit can be conveniently installed, for example, over a standard top, 
31/4".times.10" range hood knockout. It may be used to exhaust through the 
roof or through the wall (by using a right angle stack elbow) by 
connecting the appropriate ducting above the damper control transition 
section. 
Whereas the present invention has been described with respect to specific 
embodiments thereof, it should be understood that the invention is not 
limited thereto as many modifications thereof may be made. It is therefore 
contemplated to cover by the present application any and all such 
modifications as fall within the true spirit and scope of the appended 
claims.