Abstract:
A fragrance disperser in one form includes a single fan that passes air over a wicked single or double fragrance. A second form has the fan reversible to provide two different airstreams that evaporate respective different fragrances one after the other. Where two fragrances are provided, the evaporation may be by respective electrical heaters. A fragrance source may be formed by two sheets joined together to form two chambers each receiving a respective wick and having respective exposed wick portions. The source may incorporate a source of electrical power. An alternative source has a reservoir for fragrance and a wick located in an air passage forming part of the source so that an air flow is guided through the passage past the wick to evaporate fragrance. Where two fragrances are provided, the fragrance sources may be located side-by-side and matching fragrances may have, for example, matching indicia on the sources so that the match can be easily determined visually.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of application Ser. No. 12/028,071, filed Feb. 8, 2008, which is a divisional of application Ser. No. 10/491,718, filed Aug. 5, 2004, now U.S. Pat. No. 7,344,123, issued: Mar. 18, 2008 (which are hereby incorporated by reference). 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to fragrance dispersers, fragrance sources and fragrance containers. 
     Fragrance dispersers are used to release one or more fragrances into an enclosed space such as a room. In general, the fragrance is held by a fragrance source and released either by natural convection or by forced convection or by heating a wick or pad, for example, holding the fragrance. 
     BRIEF SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, there is provided a fragrance disperser comprising a source of fragrance and means for generating a flow of air to release said fragrance. 
     One form of fragrance source is a container containing a liquid fragrance. The fragrance is released by a convection air current passing across an outlet for the fragrance. It is a problem that this does not provide a directed flow of air. 
     According to a second aspect of the invention, there is provided a fragrance container comprising a reservoir for receiving a liquid fragrance and an outlet to the reservoir, the outlet defining a path for a flow of air to release fragrance in the reservoir. 
     Many fragrance sources are complicated to manufacture including separate containers and wicks. 
     According to a third aspect of the invention, there is provided a fragrance source comprising a back sheet and a front sheet with a wicking material therebetween the back sheet and the front sheet being joined together along a closed line to define a reservoir for fragrance, a portion of the wicking material being exposable outside the closed line for releasing the fragrance, the join being such as to allow the wicking material to wick fragrance from the reservoir to the exposable portion. 
     According to a fourth aspect of the invention, there is provided a fragrance disperser comprising two sources of fragrance, means for dispersing fragrance from said sources and a control system for controlling said dispersing means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following is a more detailed description of some embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:— 
         FIG. 1  is a schematic front elevation of a first form of fragrance disperser, a front cover of the disperser being removed to show a fan of the disperser and a fragrance source, the fan rotating in a first sense, 
         FIG. 2  is a similar view to  FIG. 1  but showing the fan rotating in an opposite sense, 
         FIG. 3  is a cut-away side elevation of the fragrance disperser of  FIGS. 1 and 2 , 
         FIG. 4  is a section on the line A-A of  FIG. 3 , 
         FIG. 5  is a perspective view of the fragrance source of  FIGS. 1 to 4 , 
         FIG. 6  is an exploded view of the fragrance source of  FIG. 5 , 
         FIG. 7  is a graph of time against operational state for the fragrance disperser of  FIGS. 1 to 4 , 
         FIG. 8  is a perspective view of a second form of fragrance source for use with the fragrance disperser of  FIGS. 1 and 2 , two wicks of the source being shown separated from the source for clarity, 
         FIG. 9  is an exploded view of the second form of fragrance source of  FIG. 8 , 
         FIG. 10  is a front elevation of a second form of fragrance disperser, and two fragrance sources, 
         FIG. 11  is a front elevation of the second form of fragrance disperser of  FIG. 10  with a front cover removed and showing a fan rotating in one sense, 
         FIG. 12  is a similar view to  FIG. 11  but showing the fan rotating in an opposite sense, 
         FIG. 13  is an internal view from above of the second form of fragrance disperser, 
         FIG. 14  is a cross-section on the line B-B of  FIG. 12 , 
         FIG. 15  is a similar view to  FIG. 10  showing the second fragrance disperser provided with buttons that allow different modes of operation, 
         FIG. 16  is a similar view to  FIG. 10  showing the second fragrance disperser with shutters that control the volume of fragrance dispersed, 
         FIG. 17  corresponds to  FIG. 16  but shows one of the shutters in a fully open position and the other in a partially closed position, 
         FIG. 18  is a similar view to  FIG. 11  showing the second fragrance dispenser with wick cover assemblies that control the volume of fragrance dispersed, 
         FIG. 19  corresponds to  FIG. 18  but shows one of the wick covers covering a wick to a minimum degree and the other covering another wick to a maximum degree, 
         FIG. 20  is a similar view to  FIG. 14  but with the fragrance source including a peg and the fragrance disperser including a microswitch operable by the peg, 
         FIG. 21  is a side view of a fragrance source of  FIGS. 9 to 13  and including a peg but with the fragrance and wick removed, 
         FIG. 22  is a schematic view of the fan of the second form of fragrance disperser together with a shutter, 
         FIG. 23  is a schematic cross-section of the fan and shutter of  FIG. 22  showing the parts interconnected by a frictional clutch, 
         FIG. 24  is a schematic cross-section of the fan and shutter of  FIG. 22  showing the parts interconnected by a centrifugal clutch, 
         FIG. 25  is a plan view of a first clutch part of the centrifugal clutch of  FIG. 24 , 
         FIG. 26  is a plan view of a second clutch part of the centrifugal clutch of  FIG. 24 , 
         FIG. 27  is a front elevation of a third form of fragrance disperser and two fragrance sources, 
         FIG. 28  is a front elevation of the third form of fragrance disperser with a front cover removed and showing a fan rotating in one sense, 
         FIG. 29  is a similar view to  FIG. 24  but showing the fan rotating in an opposite sense, 
         FIG. 30  is a cut away side elevation of the fragrance disperser of  FIGS. 28 and 29 , 
         FIG. 31  is a cross-section on the line C-C of  FIG. 29 , 
         FIG. 32  is a side elevation of a fragrance source for use with the third forms of fragrance disperser, a cap of the source being removed, 
         FIG. 33  is a similar view to  FIG. 32  but showing the internal structure of an outlet to the source, 
         FIG. 34  is a similar view to  FIG. 32  but showing a flow of air through the outlet to the fragrance source, 
         FIG. 35  is a side elevation of a fragrance source of the kind shown in  FIGS. 32 to 34  adjacent a second such source shown with the cap and outlet omitted, 
         FIG. 36  is a side elevation of a modified form of the fragrance source of  FIGS. 32 to 34  adjacent a second such source with the cap and outlet omitted, 
         FIG. 37  is a schematic side elevation of a fourth form of fragrance disperser including a fan and a source of a single fragrance, 
         FIG. 38  is a similar view to  FIG. 37  but with the source having two fragrances, 
         FIG. 39  is a schematic view of a fifth form of fragrance disperser including two sources of fragrance dispersed by heat and a control system, 
         FIG. 40  is a similar view to  FIG. 39  but showing an alternative method of dispersing the fragrances by heat, 
         FIG. 41  is a schematic view of a fragrance disperser of any of the kinds shown in  FIGS. 1 to 4  or  FIGS. 10 to 19  or  FIGS. 27 to 31  and mounted on a vertical surface. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to  FIGS. 1 to 4 , the fragrance disperser is formed by a housing  10 , a fan  11  and a fragrance source  12 . 
     The housing  10 , which may be formed of any suitable material such as metal or plastics, is formed by a back wall  13 , a side wall  14  and a front cover  15  (seen in  FIG. 3 ). The back wall  13  is generally rectangular with parallel side edges  16  interconnected at one end by a straight lower end edge  17  and at the other end by a generally semi-circular end edge  18 . The side wall  14  extends around the side edges  16  and the semi-circular upper end edge  18 . The portion of the side wall  14  extending around the upper end edge  18  has an interior surface  19  (see  FIGS. 1 and 2 ) formed by two-part spirals that meet at the apex of the end edge  18  and increase in radius from that point. This portion of the housing contains the fan  11  which is connected to a motor  21  by a drive shaft  22  (see  FIG. 3 ). The motor  21  is connected to, and controlled by, a control board  23  mounted on the back wall  13 . 
     The fragrance source  12  is also carried by the back wall  13  below the fan  11 . The construction of this fragrance source  12  will be described in more detail below. 
     The front of the housing  10  is closed by the front cover  15  seen in  FIGS. 3 and 4 . The cover  15  has generally the same shape as the back wall  13  but is provided with an air inlet  26  aligned with the fan  11 . In addition, as seen in  FIG. 3 , the cover is provided with an inwardly slanted wall  27  and a central divider  28 . With particular reference to  FIGS. 3 and 4 , the wall  27  and the divider  28  form a pair of side-by-side ducts  29   a ,  29   b  that converge as they extend away from the fan  11  and terminate in respective outlets one of which is shown at  30  in  FIG. 3 . The position of the divider  28  in relation to the fragrance source  12  will be discussed below. 
     The fragrance source  12  is shown in more detail in  FIGS. 5 and 6 . Referring to those Figures, the fragrance source  12  comprises a back sheet  31  which is of generally rectangular shape and may be formed, for example, from a plastics laminate. The back sheet  31  is provided with a lateral fold line  32  which divides the back sheet  31  into a main portion  33  and a flap  34 . The end of the flap  34  is provided with a tab  35  and the surface of the flap on the inner side of the fold line  32  is provided with two adhesive frames  36  whose function will be described below. 
     First and second strips  37   a ,  37   b  of wick material are placed on the inner surface of the main portion  33  of the back sheet  31 . Each strip of wick material  37   a ,  37   b  is of elongate rectangular shape provided towards one end with a pair of inwardly directed registering notches  39   a ,  39   b  whose function will be described below. As seen in  FIG. 6 , the first and second strips  37   a ,  37   b  are arranged side-by-side and parallel to one another. 
     The first and second strips  37   a ,  37   b  are covered by a front sheet  40  that may also be of a plastics laminate and is the same size as the main portion  33  of the back sheet  31 . The front sheet  40  is formed towards one edge with two windows  41   a ,  41   b . Each window is in register with a respective shorter portion of an associated one of the first and second strips  37   a ,  37   b  between the notches  39   a ,  39   b  and the adjacent end of the associated strip  37   a ,  37   b . Of course, the front sheet  40  may be formed in one-piece with the back sheet  31 , extending from the edge of the back sheet  31  opposite the fold line  32 . 
     The front sheet  40 , when not formed in one-piece with the back sheet, is then connected to the back sheet along lines  42 , 43 , 44  by, for example, welding or gluing. The first connection line  42  is a rectangular line extending around the peripheries of the main portion  33  and the front sheet  40  and thus forms a closed chamber between these parts  33 , 40 . The second connection line  43  is a longitudinal line which extends along the gap between the first and second strips  37   a ,  37   b  thus sub-dividing the main chamber to form separate chambers each containing a respective strip  37   a ,  37   b . The third connection line  44  is a lateral line extending between the side edges of the main portion  33  and the front sheet  40  with the line  44  extending into the notches  39   a ,  39   b  and being interrupted between the notches  39   a ,  39   b . Thus, each sub-chamber containing an associated strip  37   a ,  37   b  is divided into a larger portion and a smaller portion separated by a neck with the smaller portion underlying an associated window  41   a ,  41   b.    
     Each larger portion of each sub-chamber is filled with a respective different liquid fragrance. The flap  34  is folded over the windows  41   a ,  41   b  with the adhesive frames  36  sealing around the peripheries of the windows  41   a ,  41   b  to close the windows  41   a ,  41   b . Finally, an under surface of the back sheet  31  is mounted on a source of electric power  45 . This may be a flat dry cell battery. 
     In use, the fragrance source  12  is opened by pulling the tab  35  to open the peelable seal formed by the adhesive frames  36 . The fragrance source  12  is then mounted in the housing  10  as briefly described above. In this position, the windows  41   a ,  41   b  are, as seen in  FIGS. 1 and 2 , adjacent the outlets  30  with the divider  28  extending along the longitudinal connecting line  43  so that each window  41   a ,  41   b  is in a respective duct  29   a ,  29   b . Each fragrance wicks to the associated window  41   a ,  41   b  at a rate controlled both by the characteristics of the strips  37   a ,  37   b  and the gaps between the notches  39   a ,  39   b . The source of electric power  45  includes contacts which connect the source of electric power  45  to the control system  23  for the motor  21  of the fan  11 . 
     The motor  21  operates when connected to the source of electric power  45  and the fan  11  rotates in, for example, the clockwise direction shown in  FIG. 1 . This produces an air flow through the duct  29   a  associated with the first window  41   a  and so conveys the associated fragrance to the surrounding atmosphere. The convergence of the duct  29   a  towards the associated outlet  30  increases the speed of the air as it passes across the window  41   a.    
     After a period of time, the control system  23  reverses the direction of rotation of the fan  11  so that it rotates in an anti-clockwise direction as shown in  FIG. 2 . The effect of this is to pass air along the duct  29   b  and across the window  41   b  so releasing the associated fragrance through the outlet  30  into the surrounding atmosphere. 
     Referring next to  FIG. 7 , this shows one mode of operation of the fan  11  under the control of the control system  23 . T 1  is the time for which the fan  11  rotates in, for example, the clockwise direction. This time is designed to allow the concentration of the first fragrance to reach a maximum. The dwell period T 2  is designed to allow the first fragrance to disperse before the second fragrance is emitted. T 3  is the time for which the fan rotates in, for example, an anti-clockwise direction to emit the second fragrance and allow it to reach a maximum and T 4  is the dwell period that allows the second fragrance to disperse. The time for which each wick is inactive allows the fragrance to wick to the associated window for immediate evaporation when the wick becomes active. As will be seen, these intervals need not be equal. They may be varied depending on the fragrance. There is a known phenomenon called olfactory fatigue where, after a time a person smelling a fragrance at a stable concentration becomes unaware of the smell. This time varies from fragrance to fragrance and the intervals mentioned above may be adjusted in accordance with those times. In addition, the time intervals may be able to be manually adjusted by the user. Further, the control system could be programmed to accommodate small or large rooms or to provide a booster fragrance on demand. 
     The timing may be altered for different sized rooms in a number of different ways. For example, for a larger sized room, it may be desirable to increase the on times T 1 , T 3  for fragrances  1  and  2  whilst leaving the off times T 2 , T 4  (the dwell periods) unchanged. Alternatively, the cycle could be altered by leaving the on times T 1 , T 3  unchanged but shortening the dwell periods T 2 , T 4 . Another possibility is to increase both the on and off times whilst keeping the on/off ratio unchanged. Similarly for smaller rooms it may be desirable to reduce the on times T 1 , T 3  only, or to increase the dwell periods T 2 , T 4  only, or to shorten both whilst maintaining the same ratio. 
     When the fragrance source  12  is finished, it can be replaced by a new fragrance source  12  on an associated source of electric power  45 . The power of the source  45  is matched to the volume of fragrance so that when the power of the source is running low the amount of fragrance remaining is also running low. The control system  23  may monitor battery power and provide an indication when the power is running low so providing an indication that the fragrance is close to exhaustion and requires replacement. The indication may be a visual indication provided, for example, by an LED on the housing  10 . 
     A second form of fragrance source for use with the fragrance disperser of  FIGS. 1 and 2  is shown in  FIGS. 8 and 9 . The second fragrance source  46  is formed by a rectangular back sheet  47  which may be of a plastics laminate and a similar shaped front sheet  48  of the same material. Two valve inserts  49   a ,  49   b  are also provided. Each valve insert  49   a ,  49   b  is formed by a short section of tube  50   a ,  50   b  and a pair of diametrically opposed outwardly extending wings  51   a ,  51   b . Each tube  50   a ,  50   b  contains a pierceable seal (not shown). 
     The back sheet  47  is placed beneath the front sheet  48  with the valve inserts  49   a ,  49   b  spaced apart along registering edges of the sheets  47 , 48 . The sheets  47 , 48  are then connected together along lines  53 , 54  by, for example, welding or gluing. The first line  53  extends around the peripheries of the back sheet  47  and the front sheet  48  and also connects to the wings  51   a ,  51   b  and the tubes  50   a ,  50   b  of the valve inserts  49   a ,  49   b . The second line  54  is a longitudinal line extending between the edge of the sheets  47 , 48  including the valve inserts  49   a ,  49   b  and the opposite edge. The back sheet  47  and the front sheet  48  thus form between them a chamber which is sub-divided by the longitudinal line into two sub-chambers. Each chamber contains an associated different liquid fragrance. 
     The second fragrance source  46  also includes two inserts  55   a ,  55   b . Each insert  55   a ,  55   b  is formed by a generally rectangular area of wick material and an elongate capillary connector  57   a ,  57   b  projecting from the associated wick material  56   a ,  56   b.    
     In use, the seals  52  in the valve inserts  49   a ,  49   b  retain the associated fragrance in the sub-chambers. When it is wished to use the second fragrance source, each capillary connector  57   a ,  57   b  is inserted through an associated seal of a valve insert  49   a ,  49   b  to reach the fragrances in the sub-chambers. The fragrances pass along the capillary connectors  57   a ,  57   b  to the associated wick materials  56   a ,  56   b  where they evaporate. 
     The second fragrance source  46  may be mounted and used with the fragrance disperser as described above with reference to  FIGS. 1 to 4 . 
     Referring next to  FIGS. 10 to 14 , the second form of fragrance disperser has parts common to the fragrance disperser of  FIGS. 1 to 4 . Those parts will be given the same reference numerals as the corresponding parts in  FIGS. 1 to 4  and will not be described in detail. 
     In the second fragrance disperser, the fragrance is supplied by two containers  58   a ,  58   b . Each container  58   a ,  58   b  is connected to the housing  10  in a manner to be described below and includes a projecting wick  59   a ,  59   b  received in an associated shaped duct  60   a ,  60   b  formed in the housing  10 . 
     Each container  58   a ,  58   b  is formed with a neck  61   a ,  61   b  surrounding a mouth  62   a ,  62   b . Each neck has an outwardly directing flange  63   a ,  63   b  and the associated wick  59   a ,  59   b  extends out of each mouth  62   a ,  62   b . The housing is formed at the lower end edge  17  with two apertures  64   a ,  64   b  each for receiving the neck  61  of the associated container  58   a ,  58   b . As seen particularly in  FIG. 14 , each aperture  64   a ,  64   b  includes a retention mechanism for holding the associated container  58   a ,  58   b  connected to the housing  10 . The retention mechanism is formed by an inwardly directed projection  65  that extends under the flange  63   a ,  63   b  of the associated container  58   a ,  58   b  and a peg  66  that retracts against a spring  67  as the neck  61   a ,  61   b  is pushed into the associated aperture  64   a ,  64   b  to allow the flange  63   a ,  63   b  to pass the peg  66  and then is forced outwardly by the spring  67  to engage behind the flange  63   a ,  63   b  to hold the associated container  58   a ,  58   b  in position. 
     Each shaped duct  60   a ,  60   b  extends from a respective side of the fan  11  initially in a direction tangential to the fan  11 . Then, as seen in  FIG. 14  the duct  60   a ,  60   b  turns through  900  to terminate in an outlet  68   a ,  68   b  on the cover  15 . As seen in  FIGS. 11 ,  12  and  14 , each wick  59   a ,  59   b  extends along the associated duct  60   a ,  60   b  to terminate adjacent the periphery of the fan  11 . The fan  11  is associated with a shutter  69  which is carried on the drive shaft  22  and includes an arcuate wall  70 . As seen in  FIG. 11 , when the fan  11  rotates in a clockwise direction, the wall  70  of the shutter  69  closes the duct  60   b  and leaves the duct  60   a  open so minimizing the volume of air leaving the duct  60   b . When the fan  11  rotates in an anti-clockwise direction, the wall  70  of the shutter  69  closes the other duct  60   a  leaving the duct  60   b  open and so minimizing the volume of air leaving the duct  60   a.    
     The construction and operation of the shutter  69  will be described in more detail below. 
     In use, the second fragrance disperser described above with reference to  FIGS. 10 to 14 , operates broadly as described above with reference to  FIGS. 1 to 4 . Air from the fan passes along one or other of the shaped ducts  60   a ,  60   b  and evaporates fragrance from the associated wick  59   a ,  59   b  which then passes out of the associated outlet  68   a ,  68   b  into the surrounding atmosphere. The shape of the duct  60   a ,  60   b  ensures that air from the fan  11  does not pass simply axially along the wicks  59   a ,  59   b . Rather, the shape of the ducts  60   a ,  60   b  results in a circumferential flow of air around the wicks  59   a ,  59   b . This results in more efficient evaporation of fragrance from the wicks  59   a ,  59   b.    
     Power for the motor  21  is provided from an external power supply such as a battery (not shown) or a source of mains power. 
     When a container  58   a ,  58   b  is empty, it can be released from the retention mechanism and replaced by a fresh container. 
     Referring now to  FIG. 15 , parts common to  FIG. 15  on the one hand and  FIGS. 10 to 14  on the other hand will be given the same reference numerals and will not be described in detail. In this arrangement the housing  10  is provided with three control buttons  111 , 112 , 113 . On pressing the button  111 , the timing protocol is altered to be suitable for smaller rooms. Pressing the button  112  alters the timing protocol to be suitable for larger rooms. Pressing the button  113  alters the timing protocol for a set limited period of time. For that limited period of time, the volume of fragrance emitted is increased. This provides a boost of fragrance. Alternatively, instead of changing the time periods for which the fan  11  operates, the speed of the fan  11  could be increased or decreased to alter the volume of fragrance emitted. This could be achieved by the varying power supplied to the motor. 
     Other means for controlling the volume of fragrance emitted will now be described with reference to  FIGS. 16 to 19 , in which parts common to  FIGS. 10 to 15  on the one hand and to  FIGS. 16 to 19  on the other hand will be given the same reference numerals and will not be described in detail. 
     Referring first to  FIGS. 16 and 17 , the size of each duct opening  68   a ,  68   b  is controlled by a respective shutter assembly  210   a ,  210   b . Each assembly  210   a ,  210   b  comprises a shutter  211   a ,  211   b  to which is connected a peg  212   a ,  212   b  which is slidably movable in a vertical slot  213   a ,  213   b  in the front cover  15  of the disperser, such that when the peg  212   a ,  212   b  is at the top of the slot  213   a ,  213   b  the shutter is in a fully open position and the duct opening  68   a ,  68   b  is a maximum size, and when the peg is at the bottom of the slot the shutter is in a fully closed position and the duct opening is a minimum size. This may correspond to completely closing off the duct opening  68   a ,  68   b.    
     Each shutter assembly  210   a ,  210   b  may be controlled independently to control the relative volumes of each fragrance emitted. In  FIG. 16 , both shutters  211   a ,  211   b  are shown in the fully open position, and the respective pegs  212   a ,  212   b  can be seen at the top of each respective associated slot  213   a ,  213   b . In  FIG. 17 , the right-hand shutter assembly  210   a  is shown in an intermediate position, the shutter  211   a  partially restricting the associated duct opening  68   a  to reduce the volume of fragrance emitted from the associated container  58   a . In the same Figure, the left-hand shutter assembly  210   b  is in the fully open position. Thus, for a given fan speed, or a given time for which the fan  11  is operational, a greater proportion of fragrance will be emitted from container  58   b  than from container  58   a.    
     As described above, each shutter assembly is adjusted manually by means of the respective peg  212   a ,  212   b . Alternatively, the shutters  211   a ,  211   b  may be controlled electronically, in which case the pegs  212   a ,  212   b  and the slots  213   a ,  213   b  may be disposed of. 
     Referring now to  FIGS. 18 and 19 , the exposed surface area of each wick  59   a ,  59   b  is controlled by a respective wick cover assembly  220   a ,  220   b . Each wick cover assembly  220   a ,  220   b  comprises a cap  221   a ,  221   b , a cover  222   a ,  222   b  and a slider  223   a ,  223   b . The cap  221   a ,  221   b  is substantially cylindrical and is mounted on the upper surface of the associated wick  59   a ,  59   b  and includes at its lower end an annular shoulder  224 . The cover  222   a ,  222   b  is substantially cylindrical and includes at each of its upper and lower ends an inwardly projecting annular lip  225  and  226  respectively. The slider  223   a ,  223   b  is also substantially cylindrical and includes at its upper end an annular shoulder  227  and near its lower end and a horizontally projecting peg  228   a ,  228   b . The peg  228   a ,  228   b  is slidably movable in a vertical slot (not shown) in the side wall  14  of the disperser. The slider  223   a ,  223   b  is slidably mounted on the associated wick  59   a ,  59   b  and is connected to the cover  222   a ,  222   b  in the region of the annular shoulder  227  of the slider and the lower annular lip  226  of the cover. In this way, the cover  222   a ,  222   b  is slid over the cap  221   a ,  221   b  by virtue of a corresponding sliding movement of the slider  223   a ,  223   b  over the wick  59   a ,  59   b , which is, in turn, controlled manually by sliding the associated peg  228   a ,  228   b  within its associated slot. The cover  222   a ,  222   b  and the slider  223   a ,  223   b  could alternatively be combined as a single part. 
     In a first position, corresponding to that shown for both wick cover assemblies  220   a ,  220   b  in  FIG. 18  and for the right-hand wick cover assembly  220   a  in  FIG. 19 , the slider  223   a ,  223   b  is in an upper position in which the annular shoulder  227  of the slider  223   a ,  223   b  abuts the annular shoulder  224  of the cap  221   a ,  221   b . In this position, the cover  222   a ,  222   b  substantially entirely overlaps the cap  221   a ,  221   b , and the associated wick  59   a ,  59   b  is thus exposed to a maximum extent. 
     In a second position, corresponding to that shown for the left-hand wick cover assembly  220   b  in  FIG. 19 , the slider  223   b  is in a lower position in which the upper lip  225  of the cover  222   b  abuts the annular shoulder  224  of the cap  221   b . In this position, the cover  222   b  extends beyond the cap  221   b  and covers a portion of the wick  59   b . In this second position, the wick is thus exposed to a minimum extent, and for a given fan speed or a given time for which the fan  11  is operational, a lesser proportion of fragrance will be emitted than when the wick cover assembly  220   a ,  220   b  is in the first position, by virtue of the reduced exposed wick surface area. The sliders  223   a ,  223   b  may be positioned intermediate the first and second positions, and each is independently controllable to control the relative volumes of fragrance emitted from each respective container  58   a ,  58   b.    
     As with the shutter assemblies  210   a ,  210   b  of  FIGS. 16 and 17 , control of the wick cover assemblies  220   a ,  220   b  need not be manual. Indeed, it may be automatic, or electronic, in either case there being no need for the provision of the pegs  228   a ,  228   b  and their associated slots in the side wall  14 . 
     Referring next to  FIGS. 20 and 21 , the disperser of  FIGS. 10 to 14  may be modified so that the operation of the disperser is varied in accordance with information derived from the associated containers  58   a ,  58   b . Parts common to  FIGS. 20 and 21  on the one hand and to  FIGS. 10 to 14  on the other hand are given the same reference numerals and are not described in detail. In this arrangement, the flange  63   a ,  63   b  on the neck  61   a ,  61   b  of each container  58   a ,  58   b  is provided with a peg  109 . When the container  58   a ,  58   b  is engaged with the housing  10 , the peg  109  engages an associated microswitch  110 . The microswitch  110  passes a signal to the control system  23  that modifies the operation of the control system  23 . For example, when a signal is received from the microswitch, the relevant cycle times may be altered in comparison with the cycle times when the peg  109  is absent. 
     Other arrangements are possible. For example, the container may include a readable microchip or bar code that provides information to the control system  23  for adjusting the operation of the fan  11 . 
     Referring next additionally to  FIGS. 22 to 25 , these Figures illustrate various modes of operation of the shutter  69 . As seen in  FIG. 23 , the shutter  69  comprises a generally frusto-conical portion  71  with the narrower end closed by an end wall  72 . The drive shaft  22  passes through this end wall and is coaxial with the axis of the frusto-conical portion  71 . A peripheral flange  73  extends outwardly of and around the wider end of the frusto-conical portion  71  and the wall  70  extends around a portion of this flange  73 . In order to counter balance the wall  70 , the diametrically opposite portion of the flange  73  may be thickened so that the shutter  69  is in static balance around the drive shaft  22 . 
     In its simplest form of operation, the shutter  69  may be rotated only by the air flow generated by the fan  11 . When the fan  11  is rotating in an anti-clockwise direction, there will be a corresponding anti-clockwise flow of air and, due to the balance of the shutter  69 , this may be sufficient to rotate the shutter to the position shown in  FIG. 11 . Likewise, when the fan  11  rotates in a clockwise direction, there is a corresponding clockwise rotation of air which moves the shutter  69  to the position shown in  FIG. 12 . 
     There may, however, be cases where this movement cannot be achieved reliably by the use of air alone. In this case, and referring to  FIG. 23 , in an alternative arrangement, a felt washer  74  and a crimped washer  75  are provided on the drive shaft  22  between the end wall  72  of the shutter  69  and a mounting boss  76  of the fan  11  which is connected to drive shaft  22 . In this arrangement, when the motor  21  rotates in one direction, the rotational movement of the fan  11  is transmitted frictionally by the washer  74 ,  75  to the shutter  69  so rotating the shutter  69  in the same sense as the fan. The arrangement works in whichever direction the motor  21  is rotated. 
     Another possibility is shown in  FIGS. 24 ,  25  and  26 . In this arrangement, the fan  11  carries a first clutch part  77  shown in  FIG. 25 . This clutch part  77  includes three arcuate arms  78  which, as the fan  11  rotates, move from the full line position shown in  FIG. 25  outwardly to the dotted line position shown in that Figure. The shutter  69  includes a second clutch part  79  (see  FIG. 26 ) which includes three outwardly directed equi-angularly spaced projections  80 . When the arms  78  are in the full line position shown in  FIG. 25 , they engage these projections  80  so locking the first and second clutch parts  77 , 79  together and thus rotating the shutter  69  with the fan  11 . As the speed of the fan  11  increases, the arms  78  move to the dotted line position shown in  FIG. 25  where they are disengaged from the projections  80  so allowing the fan  11  to rotate independently of the shutter  69  with the shutter  69  being maintained in position by air flow (and possibly friction). 
     It will be appreciated that these are only some of the ways in which the shutter  69  can be moved. Other ways are possible. 
     Referring next to  FIGS. 27 to 31 , the third fragrance disperser has parts common with the second fragrance disperser of  FIGS. 10 to 14 . Those common parts will be given the same reference numerals and their construction and operation will not be described in detail. 
     The third fragrance disperser includes two fragrance sources  81   a ,  81   b  in which the wick is surrounded by an outlet formed by part of the source. 
     Referring particularly to  FIGS. 28 and 29 , each fragrance source  81   a ,  81   b  includes a container  82   a ,  82   b  holding a liquid fragrance and including an integral outlet  83   a ,  83   b . Each outlet  83   a ,  83   b  is formed at its end remote from the container  82   a ,  82   b  with an entrance  84   a ,  84   b  and, at a point in the outlet  83   a ,  83   b  adjacent the associated container  82   a ,  82   b , each outlet  83   a ,  83   b  is formed with an exit  85   a ,  85   b  (see  FIG. 30 ). As seen in  FIGS. 27 and 30 , these exits  85   a ,  85   b  are aligned with respective apertures  86   a ,  86   b  in the cover  15  of the housing  10 . Each outlet  83   a ,  83   b  contains an upper portion of an elongate strip shaped wick  87   a ,  87   b  whose lower end is immersed in the fragrance in the container  82   a ,  82   b . Each outlet is a snap fit in an associated shaped duct  60   a ,  60   b  of the housing  10 . 
     In use, rotation of the fan  11  in a clockwise direction produces an air flow which is forced through the first duct  60   a  and enters the entrance  84   a  of the outlet  83   a  of the associated fragrance source  81   a . The air then passes over and around the wick  87   a  releasing fragrance which then passes through the exit  85   a  and through the aperture  86   a  of the cover  15  to the surrounding atmosphere. Anti-clockwise rotation of the fan  11  produces, as seen in  FIG. 25 , a flow of air through the entrance  84   b  of the outlet  83   b , past the associated wick  87   b  and then through the exit  85   b  and the cover aperture  86   b.    
     The cover apertures  86   a ,  86   b  may be provided with respective shutter assemblies as described above with reference to  FIGS. 16 and 17 . 
     When a fragrance source  81   a ,  81   b  is empty, it can be replaced by a fresh fragrance source. 
     In this embodiment, the wick  87   a ,  87   b  is packaged within and protected by the outlet  83   a ,  83   b . The air duct is part of the fragrance source  81   a ,  81   b  and is thus a consumable. Each wick  87   a ,  87   b  may be provided with a wick cover assembly similar to those described above with reference to  FIGS. 18 and 19 , but adapted for consumable fragrance sources. 
     Referring next to  FIGS. 32 ,  33  and  34 , there is shown a fragrance source of a kind for use with the third form of fragrance disperser described above with reference to  FIGS. 27 to 31 . The fragrance source is formed by a container  88  comprising a reservoir  89  and an outlet  90 . The parts may be formed from any suitable material such as a plastics material or glass. As seen in  FIG. 34 , the outlet  90  is formed at its end remote from the reservoir  89  with an entrance  91  and, at a point in the outlet  90  adjacent the reservoir  89 , the outlet  90  is formed with an exit  92 . A wick  93  leads from the reservoir  89  and terminates in the outlet  90  adjacent the entrance  91 . 
     The reservoir  89  contains a fragrance. A shaped cap  94  covers the outlet  90 . 
     This container  88  can be used with the fragrance disperser of  FIGS. 27 to 31 . The cap  94  is removed and the outlet  90  inserted into the housing  10 . Air is then passed through the outlet  90  via the entrance  91  as described above. The air then leaves via the exit  92 . 
     It will be seen from  FIGS. 27 to 31 , that, when mounted on the housing  10 , the fragrance sources  81   a ,  81   b  are side-by-side. It will be appreciated that these two fragrance sources  81   a ,  81   b , may contain different fragrances. Not all pairs of fragrances are perceived by the nose as being complementary and it is plainly desirable to avoid combinations that are perceived as non-complementary. 
     Proposals for overcoming this are shown in  FIGS. 35 and 36 . 
     Referring first to  FIG. 35 , two containers  88   a ,  88   b  are provided of the kind described above with reference to  FIGS. 32 to 34 . A first container  88   a  is provided with a surface pattern  95  that forms a continuous pattern with a corresponding pattern  96  on the second container  88   b , with the pattern being continuous across the junction between adjacent side surfaces  97   a ,  97   b  of the containers  88   a ,  88   b . These containers  88   a ,  88   b  are arranged to contain complementary fragrances (i.e. fragrances that are complementary in an olfactory sense) and any container containing a non-complementary fragrance has a different pattern which does not match the pattern of either of the containers in  FIG. 30 . Thus, if a container including a non-complementary fragrance is used with one of the containers illustrated in  FIG. 30 , the lack of matching pattern will be readily apparent. It will be appreciated that this effect need not be provided by a raised pattern. Inset patterns may be used or simply print effects. 
     Another possibility is provided by the arrangement of  FIG. 36 . In this Figure, one side surface  97   a  of one container  88   a  has a non-planar shape which is complementary with a non-planar shape of the side surface  97   b  of the other container  88   b  containing a complementary fragrance so that the side surfaces  97   a ,  97   b  interlock when the containers  88   a ,  88   b  are placed side-by-side in the housing  10 . Containers holding non-complementary fragrances are provided with different side surface configurations and so will not be able to interlock and will thus not be able to be used. 
     The use of a fan to disperse fragrance need not be confined to the dispersal of two fragrances. Referring next to  FIG. 37 , a fourth form of fragrance disperser is formed by a housing  98  including a chamber having an inner wall  99  formed as a spiral of increasing radius and leading to an outlet  100  extending tangentially from the wall  99 . A fan  101  is mounted in the housing  98  and is driven by a motor (not shown). The outlet contains a fragrance source  102  which may be formed by a half of the fragrance source described above with reference to  FIGS. 5 and 6 . The window  41   a  lies within the outlet  100  and rotation of the fan passes air across the window  41   a  to evaporate the fragrance. 
     In this embodiment, the fan  101  rotates in one direction only and so can be designed to be of high efficiency. The motor is controlled by a manually operated switch to give fragrance on demand. The motor is powered by a source of electric power of the kind described above with reference to  FIGS. 5 and 6 . 
     A variation of this embodiment is shown in  FIG. 38 . Parts common to  FIG. 37  and to  FIG. 38  are given the same reference numerals and are not described in detail. 
     In the embodiment of  FIG. 38 , the fragrance source is identical to the fragrance source of  FIGS. 5 and 6  with both windows  41   a ,  41   b  being within the outlet  100 . The two fragrances in the fragrance source are chosen to combine at the point of dispersion to give a desired single fragrance. This arrangement is particularly useful where the desired fragrance is formed of components that degrade if kept together. By combining them only at the point of dispersion, this degradation is avoided. 
     Of course, the fragrance source of  FIGS. 8 and 9  could also be used with either of these embodiments. Also, the size of the window  41   a ,  41   b  may be controlled by an arrangement similar to that described above with reference to  FIGS. 16 and 17 . 
     Where two fragrances are to be evaporated alternately, the evaporation need not be by a forced air flow. Referring next to  FIG. 39 , a fifth form of fragrance disperser includes two sources of fragrance  103   a ,  103   b . Each source  103   a ,  103   b  includes a container  104   a ,  104   b  and an associated wick  105   a ,  105   b  projecting from the associated container  104   a ,  104   b . Each wick  105   a ,  105   b  is surrounded by an associated heater  106   a ,  106   b . Each heater  106   a ,  106   b  is connected to a control board  107  which in turn is connected to an external power supply (not shown). The control board passes current to the heaters  106   a ,  106   b  in accordance with a predetermined programme. As each heater receives current, its temperature rises and this in turn evaporates fragrance from the associated wick  105   a ,  105   b . The control board may be arranged to provide a cycle of evaporation similar to that shown in  FIG. 7 . In addition, controls may be provided for different timing protocols as described above with reference to  FIG. 15 . Also, varying the power supply varies the temperature of the heater and thus the volume of fragrance evaporated. 
     An alternative arrangement is shown in  FIG. 40 . Parts common to  FIGS. 39 and 40  are given the same reference numerals and are not described in detail. In this embodiment, the heaters  106   a ,  106   b  are omitted and the wicks  108   a ,  108   b  are formed of or include an electrically conductive material which is connected to the control board  107 . Accordingly, when electrical current is supplied to either wick  108   a ,  108   b , the temperature of the wick is raised to evaporate fragrance. 
     Any of the fragrance dispersers described above with reference to  FIGS. 1 to 4  or  10  to  19  or  27  to  31  may be mounted on a wall. Referring next to  FIG. 41 , parts common to those Figures and to  FIG. 41  will not be described in detail and will be given the same reference numerals. Referring to  FIG. 41 , the cover  15  is continuous with the air inlet  26  omitted. Instead, an air inlet  114  is provided on the back wall  13 . In addition, an electrical connector  115  projects from the back wall  13  and includes pins, one of which is shown at  116  received in an electrical socket on a vertical surface  117  such as a wall to support the fragrance disperser and provide electrical power. The location of the air inlet  114  is a safety feature since it prevents, for example, fingers being inserted into the path of the fan  11 .