Abstract:
Disclosed is a device suitable for dispensing air treatment chemicals by heating a substrate impregnated with the chemicals. The device has a heater in the form of a table where a face of the table radiates heat directly to the impregnated substrate. The substrate releases the air treatment chemical back towards the heater. A transverse air pathway permits venting of the volatile chemical. Also disclosed are methods for assembling such devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH/DEVELOPMENT  
       [0002]     Not applicable  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates to devices that dispense a volatile air treatment chemical by heating a substrate that is impregnated with, or coated with, the chemical. More particularly it relates to such devices that efficiently use heat and are easily assembled.  
         [0004]     Substrates (particularly porous substrates) have previously been used as carriers for air treatment chemicals such as insect control agents (insecticides, insect repellents, insect growth regulators, attractants, synergists, etc.), fragrances and deodorizers. See e.g. U.S. Pat. No. 6,551,560. The disclosure of this patent, and of all other patents referred to herein are incorporated by reference as if fully set forth herein.  
         [0005]     Upon heating of the substrate a volatile air treatment chemical is caused to be dispensed from the substrate. The heating source is typically an electrical heater, but may instead be a flame in some cases.  
         [0006]     A variety of air treating functions can be achieved with such devices. For example, a porous substrate impregnated with volatile insecticide can be used to inhibit mosquito biting in a confined bedroom. Alternatively, a deodorizing or other odor control material can be dispensed to overcome malodors, or to simply provide a desired fragrance.  
         [0007]     One problem with such devices is that the substrate usually rests against a heater. The heater heats the substrate, causing the volatized air treatment chemical to be driven off the substrate in a direction away from (essentially perpendicular to) a heater surface. This can create inefficiencies. For example, the portion of the substrate adjacent the heater can act as an insulator for the portion of the substrate which is releasing the active, making control of the dispensing more difficult.  
         [0008]     Another problem with such devices is that it may take too long after usage begins to adequately treat the air in a defined environment adjacent the device. For example, when someone is about to go to bed they may activate the device in a bedroom. It is undesirable for them to have to wait a long period before feeling secure about insect protection in the room. If the heater must heat the entire vertical expanse of the substrate prior to dispensing being most efficient from a surface directed away from the heater, that can delay the start-up coverage.  
         [0009]     In other developments U.S. patent application publication 2002/0066798 disclosed the use of a type of snap fit connection in assembling a scent dispenser. However, that assembly was unduly complex.  
         [0010]     Thus, to date prior art heating dispensers for dispensing air treatment chemicals were not optimal with regard to how heat was applied to the substrate or how the construction was assembled. Devices which addressed these concerns therefore continue to be desired.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     In one aspect the invention provides an air treatment chemical dispensing device that can, upon mounting a substrate bearing a volatile air treatment chemical thereto, dispense the air treatment chemical from the substrate. The device has a housing and a heater positioned in the housing. The heater is in the form of a table having a facing wall, and is capable of radiating heat from at least the facing wall. There are means for mounting the substrate adjacent the facing wall so that when heat is radiated from the facing wall it will radiate at least in part towards the substrate to cause the substrate to release the air treatment chemical at least partially towards the facing wall.  
         [0012]     The mounting means is preferably a mechanical one (e.g. resilient fingers). However, it could be any other suitable means for mounting such as adhesives, fasteners and other mechanical retainers.  
         [0013]     In any event, there is also an air pathway structure in and through the housing permitting air to pass into the housing between the facing wall and the substrate (if such a substrate is mounted in the housing by the mounting means), and then out of the housing.  
         [0014]     In a particularly preferred form the heater also has a side wall structure capable of radiating heat there from into a portion of an air pathway structure. This is used with an air pathway structure that has an inlet vent and an outlet vent, these vents being preferably located on opposed lateral sides of the device. In this manner air can be drawn in one vent, pass partially across the lateral sides of the heater, pass partially across the facing wall of the heater, and then out the outlet. The air near the substrate will mix with the released air treatment chemical. The treated air will then be released out the outlet.  
         [0015]     This transverse air pathway is particularly desirable because the flow is at least in part between the heater and the substrate. Also, because the inlet vent can be at the bottom of the device (as the device is positioned when plugged into a vertical outlet), the heated air will naturally rise towards the outlet, further improving flow efficiency.  
         [0016]     When the substrate is mounted as in this manner, it is most preferred that it have a projecting nose positioned in contact (or near contact) with the facing wall. The remainder of the substrate will not be in contact with the heater. Thus, heat can be directly transferred to the nose, while additional heated air passes around the nose between the substrate and the heater.  
         [0017]     The volatile air treatment chemical can be selected from the group consisting of insect control agents, fragrances, and deodorizers. For example the volatile air treatment chemical can be an insect control agent which is selected from the group consisting of natural pyrethrins, pyrethrum extract, synthetic pyrethroids, other volatile insect control agents, and mixtures thereof.  
         [0018]     In another form the invention provides an air treatment chemical dispensing device that can, upon mounting a substrate bearing a volatile air treatment chemical thereto, dispense the air treatment chemical from the substrate. The device has a housing, an electrical plug structure mounted in the housing with a portion extending rearwardly outward there from, a heater linked to the electrical plug structure in the housing, and a cover unit for covering the heater which is mountable to the housing. The cover unit is configured to be suitable to mount the substrate such that the substrate has a first wall of the substrate facing the heater while a second wall of the substrate, on a side of the substrate opposite to the first wall, is essentially covered by the cover unit.  
         [0019]     Such a structure permits easy assembly which can be automated at low cost. For example, the housing, electrical plug structure, heater and cover unit can be assembled by relative axial movement there between, preferably with a snap fitting telescoping connection as part of the assembly.  
         [0020]     In yet another form, the invention provides methods of assembling such devices. One can place the electrical plug structure in the housing with a portion extending rearwardly outward there from. One then places the heater in the housing and moves it axially until it telescopes with the electrical plug structure. One then mounts the cover unit to the housing while the cover unit has the substrate positioned thereon.  
         [0021]     The substrate is preferably coated with or impregnated with a volatile air treatment chemical. In a most preferred version the substrate is configured such that it tends to wick air treatment chemical towards the heater. This could occur because the substrate comprises granular sand particles bound to a phenolic resin, where the particle size is smaller at the portion of the substrate adjacent the heater.  
         [0022]     It should be appreciated that the devices of the present invention are inexpensive to produce, and use heat extremely efficiently. The foregoing and other advantages of the present invention will be apparent from the following description. In the description that follows reference is made to the accompanying drawings which form a part thereof, and in which there is shown by way of illustration, and not limitation, expected preferred embodiments of the invention. Such embodiments do not necessarily represent the full scope of the invention, and reference should therefore be made to the claims herein for interpreting the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is a frontal, right perspective view of an air treatment device of the present invention, plugged into a vertical wall;  
         [0024]      FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1 , albeit with an indicator unit  26  removed;  
         [0025]      FIG. 3  is an exploded view of the  FIG. 2  device;  
         [0026]      FIGS. 4A-4C  illustrate a portion of a preferred method of assembly of a housing, an electrical plug structure, and a heater of the present invention; and  
         [0027]      FIGS. 4D and 4E  illustrate further steps of assembly of a device of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     Referring first to  FIG. 1 , an air treatment device  10  has an outer housing  12  comprising a rear portion  12 A and a frontal portion  12 B. An electrical prong structure  14  is positioned in the housing  12 , in the rear portion  12 A, and has a rearward end extending rearwardly outwardly there from.  
         [0029]     There is also a cover unit  18  mounted to the frontal housing portion  12 B. The cover unit  18  mounts a substrate  22  (see especially  FIG. 2 ) such that the substrate is essentially outwardly frontally covered, but is open towards the interior of the housing.  
         [0030]     In a particularly preferred version there is a separately installable indicator unit  26  removably mountable to the cover unit  18  so as to project outwardly and forwardly. The indicator unit  26  is preferably removable from the cover unit  18 , and houses a separate indicator chemical in a cup-shaped structure  44 , which may indicate to a user the amount of air treatment chemical remaining in the substrate  22 . The indicator unit  26  may have a removable lid  42  with an easy-grab tab  47 . The rear of the indicator unit  26  may extend into a well  38  formed in the cover unit to facilitate some heat transfer through wall  48  to the indicator unit.  
         [0031]     The device  10  is most preferably plugged into an electric socket on a vertical wall  16 . The directional terms in this patent are used with that type of installation in mind. However, appropriate electric sockets on horizontal or other surfaces may also be used to provide power. Thus, the terms such as “front”, “rear” “upper”, “lower”, and “side” should be interpreted in an analogous manner when the devices are used for that type of installation.  
         [0032]     The electrical prong structure  14  shown in the figures are merely for purposes of example. Cylindrical prongs of this type are suitable for linking to electric power in some countries. However, in other countries blade prongs, or mixtures of blades, cylinders and other shaped prong elements will be used to supply the linkage to the available power (as is well recognized in the art).  
         [0033]     The frontal housing  12  has a series of elongated vents  30  on its upper and lower sides. The vents  30 A form an inlet part of an air pathway, by allowing air from the environment to enter. Air then passes as shown by the arrows in  FIG. 2 .  
         [0034]     Note that the heater  56  is in the form of a table having a frontal facing wall  61  and a side wall structure  63 . Heat can radiate towards the substrate  22 , and also sideways around the table. Thus, air entering the vents  30 A will heat up very quickly and efficiently.  
         [0035]     Note also that the nose projection  25  on the substrate  22  can be in direct contact with the facing wall  61 . This permits direct heat transfer. Nevertheless, additional heat can be applied along the sides of the nose as the somewhat heated air passes between the wall  65  of the substrate that faces the table and the facing wall  61 .  
         [0036]     This is particularly effective in causing a very fast burst of insecticide or other air treatment chemical when the device is first turned on. Hence, a room can be rendered adequately treated quite quickly. Also, where the substrate  22  is of the type that wicks the air treatment chemical towards the wall  65 , the burst can be repeated after the device has been shut off for a day and then turned on again.  
         [0037]     After the air treatment chemical has been released into the air adjacent facing wall  61 , it will pass generally transversely along the facing wall  61  until it exits outlet vent  30 B. This then treats the surrounding environmental air with the air treatment chemical.  
         [0038]     While the preferred substrate shape is a substrate having a forward frustum shaped section  23  and a rearward projecting nose  25 , other shapes can be used, with or without a projecting portion. The substrate  22  is preferably completely impregnated with a volatile air treatment chemical capable of being dispensed from the substrate  22  when the substrate  22  is heated. However, as an alternative to being completely impregnated with the air treatment chemical, the substrate  22  may instead be only partially impregnated or just coated with the chemical.  
         [0039]     The housing  12  of the overall device  10  encloses the table-shaped heater with a sufficient insulation gap to the outer housing wall to prevent the side wall from heating too much. The heater is preferably activated by inserting the rearward end of the electrical prong structure  14  into an outlet. Heat from the heater  56  may also be permitted to pass against other surfaces of the cover unit  18  through a series of openings  32  and  36  (see  FIG. 4D ). Note that wall  48  effectively closes off air dispensing through the front of the device.  
         [0040]     Referring next to  FIG. 3 , from top to bottom (forward to rear in the installed device), the device  10  has a removable cover unit  18  (shown here without the indicator unit  26 ) which, lockingly engages with the heater  56 , in a subassembly, after positioning the substrate in the cover unit. This can be achieved with a snap fit connection, or by a bayonet connection, or by other means.  
         [0041]     A heater enclosure wall  56 A is linked to an aluminum contact  60 , a thermal cutoff (TCO)  62 , a thermistor  64 , a neon in use light  70 , and a resistor  72 , all of which telescopingly, matingly engage with the underside of the heating enclosure wall  56 A. The TCO  62  and light  70  each have an end which matingly engage with corresponding silicon sleeves  74 , which in turn snap into corresponding holes in the housing  12 . A star contact  66  is preferably inserted between the aluminum contact  60  and one of two plug decks  68  forming a pin bridge  69 . In turn, the pin bridge  69  preferably snaps into the housing  12 , thereby completing the device  10 .  
         [0042]     It should be appreciated that the main components of the assembly can be assembled without tools, and in most cases with simple axial relative movement. This makes the production of the device extremely inexpensive.  
         [0043]     Once the device is plugged in, the electric current moves through the electrical prong structure  14  to drive the heater and the on light  70 . Overheating is prevented by the TCO.  
         [0044]     The heater enclosure wall  56 A may be made of any material suitable for the environment (e.g. heat resistant metals, plastics and the like). While the heater can be of many forms, a resistance heater is preferred. However, in some forms a flame, catalytic burner, or other combustion source may heat the table.  
         [0045]     Further, while a variety of resistance elements may be used, we prefer a low resistance thermistor  64 , which has a positive temperature coefficient in which the zero-power resistance increases with an increase in temperature.  
         [0046]     Referring next to  FIGS. 4A-4E , the telescopic, snap-fit assembly method of the device  10  is depicted. In the most preferred form each piece of the device  10  preferably telescopically fits together, and in some cases the parts snap fit together to lock the assembly together. In use, the on light  70  telescopingly engages an opening  57  within the heater enclosure wall  56 A configured to accommodate the on light  70 . When the light  70  is properly positioned in the opening  57 , the light  70  snaps into position, thus securing the light  70  to the heater enclosure wall  56 A. When the light  70  is snapped in place, the star contact  66  is telescopingly inserted into a plug deck  68  of the pin bridge  69  and snapped in place. At the same time, the pin bridge  69  is inserted into the housing  12  and snapped in place.  
         [0047]     The electrical prong structure  14  includes a bridge  69 . The electrical prong structure is pulled through the rearward end of the housing  12  until the prongs snap in place (see  FIG. 4B ). This pulls the heater enclosure wall  56 A over the contact  60 , TCO  62 , thermistor  64  and resistor  72 . The heater enclosure wall  56 A is preferably pushed down towards the housing  12 , past retaining beads (not shown) until the heater enclosure wall  56 A snaps into place in the housing  12  (see  FIG. 4C ).  
         [0048]     Once the heater enclosure wall  56 A is secured in the housing  12 , the cover unit  18  (with the substrate  22  included) is preferably inserted into corresponding openings on the housing (not shown) by pressing firmly downward until the cover unit  18  snaps into place. Finally, an optional indicator unit  26  or other decorative plate (not shown) may be screwed into place on the front of the cover unit  18  by engaging the legs  40  of the indicator unit with corresponding openings  43  defined by the cover unit  18 .  
         [0049]     Similarly, legs (not shown) of the cover unit  18  permit a quick, snap-fit  30  attachment to the housing  12  via corresponding grooves  50  in the housing  12 . See e.g.  FIG. 4E .  
         [0050]     Examples of a suitable substrate  22  include but are not limited to porous sand with a binder such as novolac resin, urethane resins or highly cross linked thermoplastics such as cross linked polyethylene. Particularly preferred sand substrates can be made in a fashion analogous to the sand wicks described in U.S. patent application publication 2005/0284952. Alternative substrates include other particulates such as metal, cellulose, and ceramic particulates.  
         [0051]     The air treatment chemical is preferably an insecticide, fragrance and/or disinfectant. In some cases more than one air treatment chemical may be used alone or in combination in the substrate  22 .  
         [0052]     When the air treatment chemical is an insecticide and/or insect repellent, organic phosphorous insecticides, lipidamide insecticides, natural repellents as citronella oil, natural pyrethrins and pyrethrum extract, and synthetic pyrethroids are preferred. Suitable synthetic pyrethroids are acrinathrin, allethrin as D-allethrin, PynaminR™, benfluthrin, bifenthrin, bioallethrin as Pynamin ForteR™, S-bioallethrin, esbiothrin, esbiol, bisoresmethrin, cycloprothrin, cyfluthrin, beta-cyfluthrin, cyhalothrin, lambda-cyhalothrin, cypermethrin, alpha-cypermethrin, beta-cypermethrin, cyphenothrin, deltamethrin, empenthrin, esfenvalerate, fenpropathrin, fenvalerate, flucythrinate, taufluvalinate, kadethrin, permethrin, phenothrin, prallethrin as EtocR™, resmethrin, tefluthrin, tetramethrin, tralomethrin, metofluthrin, or transfluthrin. Other volatile insecticides, such as those described in U.S. Pat. No. 4,439,415, can also be employed.  
         [0053]     In particularly preferred versions the volatile insecticide is selected from the group consisting of transfluthrin, metofluthrin, vapothrin, permethrin, prallethrin, tefluthrin and esbiothrin. Transfluthrin is the most preferred insecticide.  
         [0054]     Possible solvents for carrying these air treatment chemicals include, but are not limited to, ISOPAR™C, ISOPAR™E, ISOPAR™L, heptane, methanol, acetone, ethanol, isopropyl alcohol, dodecene and tetraydrofuran. ISOPAR™C, ISOPAR™E and ISOPAR™L are hydrocarbon solvents of varying chain length and are available from Exxon Chemical Company.  
         [0055]     Typically, volatile insect control agents will be carried in an organic solvent such as a hydrocarbon. One particularly desirable impregnation formulation for mosquito control is 50 wt. percent transfluthrin dissolved in ISOPAR C, hydrocarbon. Alternatively and often preferably, transfluthrin can first be warmed to liquefy it and then applied neat to a warmed substrate.  
         [0056]     A wide variety of volatile fragrances may be used which may optionally also have insect control attributes. Alternatively, some fragrances may be selected that provide a deodorizing function (e.g. certain terpenes). For example, various natural and artificial perfumes may be used. Non-limiting examples of these perfumes include animal-based and plant-based natural perfumes, and artificial perfumes such as alcohols, phenols, aldehydes, ketones, terpenes, and esters  
         [0057]     When an volatile air treatment chemical is a disinfectant, preferred disinfectants include, but are not limited to, glycols, trimethylene and dipropylene. Organic acids compatible with the use of the substrate  22  and environment may also be used.  
         [0058]     While the preferred embodiment of the present invention has been described above, it should be appreciated that the invention could be used in a variety of other embodiments. For example, the vent holes need not be placed on the transverse sides of the housing. Thus, the principles of the present invention can be applied in a wide variety of other ways apart from those specifically noted herein. Still other modifications may be made without departing from the spirit and scope of the invention. Thus, the claims (rather than just the preferred embodiment) should be reviewed in order to understand the full scope of the invention.  
       INDUSTRIAL APPLICABILITY  
       [0059]     The present invention provides air treatment devices having efficient heater assemblies, which are easy to manufacture.