Patent Publication Number: US-2017350416-A1

Title: Fan assembly

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/938,957, filed Jul. 10, 2013, which claims the priority of United Kingdom Application No. 1212323.8, filed Jul. 11, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a fan assembly and a stand for a fan assembly. 
     BACKGROUND OF THE INVENTION 
     A conventional domestic fan typically includes a set of blades or vanes mounted for rotation about an axis, and drive apparatus for rotating the set of blades to generate an air flow. The movement and circulation of the air flow creates a ‘wind chill’ or breeze and, as a result, the user experiences a cooling effect as heat is dissipated through convection and evaporation. 
     Some fans, such as that described in U.S. Pat. No. 5,609,473, provide a user with an option to adjust the direction in which air is emitted from the fan. In U.S. Pat. No. 5,609,473, the fan comprises a base and a pair of yokes each upstanding from a respective end of the base. The outer body of the fan houses a motor and a set of rotating blades. The outer body is secured to the yokes so as to be pivotable relative to the base. The fan body may be swung relative to the base from a generally vertical, untilted position to an inclined, tilted position. In this way the direction of the air flow emitted from the fan can be altered. 
     WO 2010/100451 describes a fan assembly which does not use caged blades to project air from the fan assembly. Instead, the fan assembly comprises a cylindrical stand which houses a motor-driven impeller for drawing a primary air flow into the stand, and an annular nozzle connected to the stand and comprising an annular air outlet through which the primary air flow is emitted from the fan. The nozzle defines a central opening through which air in the local environment of the fan assembly is drawn by the primary air flow emitted from the air outlet, amplifying the primary air flow. 
     The stand comprises a base and a body mounted on the base. The body houses the motor-driven impeller. The body is secured to the base so that that body can be moved relative to the base from an untilted position to a tilted position by pushing or sliding the body relative to the base. The base has a concave upper surface upon which are mounted a plurality of L-shaped rails for retaining the body on the base, and for guiding the sliding movement of the body relative to the base as it is moved to or from a tilted position. The body has a convex lower surface upon which a convex tilt plate is mounted. The tilt plate comprises a plurality of L-shaped runners which interlock with the rails on the base as the tilt plate is secured to the base so that flanges of the runners are located beneath conformingly shaped flanges of the rails. 
     The base further comprises a plurality of support members for supporting the body on the base. Each support member comprises a ball bearing and a spring which urges the ball bearing away from the support. The tilt plate comprises curved races for receiving the bearings and within which the bearings move as the body is tilted relative to the base. The spring force of the springs urges the body away from the base, against the weight of the body, nozzle and internal components of the body, which in turn urges together facing surfaces of the flanges of the rails and the runners so that the body is maintained in a desired tilted position by virtue of friction between the rails and the runners. 
     A problem associated with this mechanism for maintaining the body in a tilted position relative to the base is that, depending on the material from which the springs are formed, relaxation of the springs over time can cause the body to move gradually closer to the base, reducing the friction forces between the rails and the runners. If this relaxation is severe, this can compromise the ability of the mechanism to maintain the body in a tilted position. 
     SUMMARY OF THE INVENTION 
     In a first aspect the present invention provides a fan assembly comprising a base; a body mounted on the base for movement relative thereto between an untilted position and a tilted position, the body comprising at least one air inlet, an impeller and a motor for driving the impeller to draw an air flow through said at least one air inlet; at least one air outlet; an interior passage for conveying air to said at least one air outlet, the interior passage extending about an opening through which air from outside the fan assembly is drawn by air emitted from said at least one air outlet; a brake connected to the base for movement relative thereto; a stop member connected to the base; a section of the body being disposed between the brake and the stop member; and means for urging the brake towards the stop member to urge the section of the body against the stop member to maintain the body in a tilted position relative to the base by means of friction between the section of the body and the stop member. 
     The present invention thus replaces the support members of the base of the fan assembly of WO 2010/100451 with a brake and a stop member connected to the base, with a section of the body being located between the brake and the stop member. The brake and the stop member are preferably located on the upper surface of the base. The brake is preferably mounted on the upper surface of the base, or on features connected to the upper surface of the base, for sliding movement relative to the upper surface of the base. The stop member may protrude upwardly from, and may be integral with, the upper surface of the base. The section of the body is preferably connected to a lower surface of the body. The brake is biased toward the stop member so that the section of the body is pushed by the brake against the stop member. The pushing of the section of the body against the stop member generates friction forces of sufficient magnitude to resist movement of the section of the body relative to the stop member, and thus resist movement of the body relative to the base. As the brake is not required to support the weight of the body and its internal components, the degree of relaxation of the spring over the lifetime of the fan assembly can be relatively low, and so the variation in the friction forces generated between the body and the base over the lifetime of the fan assembly can be relatively low. 
     The body is preferably slidable relative to the base between the untilted position and the tilted position. This can enable the body to be easily moved relative to the base, for example by either pushing or pulling the body relative to the base, between the tilted and untilted positions. In a preferred embodiment, the brake is moveable relative to the base in a direction which is substantially orthogonal to the direction of the tilting, or sliding, movement of the body relative to the base. This direction is preferably substantially orthogonal to an axis of rotation of the impeller when the body is in the untilted position, and is preferably a horizontal direction when the fan assembly is located on a horizontal surface. 
     One or more components may be provided between the brake and the section of the body, and one of these components may engage the section of the body to urge it towards the stop member. However, in a preferred embodiment the brake is arranged to engage directly the section of the body. 
     The section of the body preferably comprises a first side surface and a second side surface located opposite to the first side surface. The brake is preferably configured to engage the first side surface and the stop member is preferably configured to engage the second side surface. The parts of the first side surface and the second side surface which are engaged by the brake and the stop member respectively over the range of the tilting movement of the body relative to the base are preferably substantially parallel so that there is substantially no variation in the frictional force generated between the body and the base over the range of tilting movement. The side surfaces are preferably parallel over substantially the entire length of the moveable member. In a preferred embodiment, the stop member comprises a first rail, and the section of the body comprises a second rail extending substantially parallel to the first rail. Preferably, each rail extends in a direction which is parallel to the direction of movement of the body relative to the base. The first rail is preferably upstanding from the upper surface of the base, and the second rail preferably depends from a lower surface of the body. 
     Preferably, the fan assembly comprises an interface between the base and the body, and at least the outer surfaces of the base and the body which are adjacent to the interface have substantially the same profile. The interface preferably has a curved, more preferably undulating, outer periphery. Facing surfaces of the base and the body are preferably conformingly curved. The base preferably has a curved upper surface, whereas the body preferably has a conformingly curved lower surface. For example the upper surface of the base may be convex, whereas the lower surface of the body may be concave. Each rail is preferably curved, and is preferably arcuate in shape. 
     In a preferred embodiment the outer surfaces of the base and the body have substantially the same profile. For example, the profile of the outer surfaces of the base and the body may be substantially circular, elliptical, or polyhedral. 
     The brake and rails are preferably enclosed by the outer surfaces of the base and the body when the body is in the untilted position. This can enable the fan assembly to have a tidy and uniform appearance, and can inhibit the ingress of dust and dirt between the rails which could otherwise reduce the friction between the rails. 
     The brake is preferably connected to the upper surface of the base. The base preferably comprises means for inhibiting movement of the brake away from the upper surface of the base. This can ensure that the brake is not moved relative to the upper surface of the base as the body is moved relative to the base so that there is no variation in the direction of the force applied to the second rail by the brake. The means for inhibiting movement of the brake away from the upper surface of the base preferably comprises a plurality of guide rails connected to the upper surface of the base, with the brake being secured to the guide rails for sliding movement along the guide rails. The brake preferably comprises a pair of side arms which each extend over and partially about a respective guide rail. The guide rails are preferably aligned orthogonally to the first and second rails. 
     The fan assembly preferably comprises a seat connected to the base, with the means for urging the brake towards the stop member being located between the seat and the brake. The seat is preferably connected to the upper surface of the base. The means for urging the brake towards the stop member preferably comprises a spring, although any other resilient element may be provided between the seat and the brake. 
     The fan assembly preferably comprises means for indicating to the user, as the body is moved relative to the base, that the body is in the untilted position. The indicating means is preferably arranged to provide a variation in the force, more preferably a reduction in the force, required to move the body relative to the base as the body moves into the untilted position. For example, the section of the body may comprise a recess, which is located on the first side surface of the section of the body which faces the brake. Part of the brake is preferably located within the recess when the body is in the untilted position. The movement of the brake into the recess as the body is moved towards the untilted position can be identified by the user through a sudden reduction in the force required to move the body relative to the base, due to a relaxation of the spring or other means for urging the brake towards the stop member. This can provide an indication to the user that the body in its untilted position relative to the base. 
     The body preferably comprises a plate connected to a lower surface of the body. The, or each, rail of the body preferably forms part of this plate. The plate is preferably connected to a recessed portion of the body so that a side wall of the body surrounds the outer periphery of the plate. 
     The fan assembly preferably comprises a plurality of pairs of interlocking members for retaining the body on the base. Each pair of interlocking members preferably comprises a first interlocking member located on the base and a second interlocking member located on the body and which is retained by the first interlocking member. The brake and the rails are preferably located between the pairs of interlocking members. Each of the interlocking members preferably comprises a curved flange which extends in the direction of movement of the body relative to the base. The flanges of each pair of interlocking members preferably have substantially the same curvature. During assembly, the flange of the second interlocking member is slid beneath the flange of the first interlocking member so that the flange of the first interlocking member prevents the body from being lifted from the base. Where the body comprises a plate, the second interlocking members are preferably connected to or otherwise form part of that plate. During assembly, the flanges of the second interlocking members are slid beneath the flanges of the first interlocking members before the plate is secured to the lower surface of the body. 
     The body preferably comprises means for inhibiting the movement of the body relative to the base beyond a fully tilted position. This also prevents the flanges of the second interlocking members from becoming separated from the flanges of the first interlocking members. The movement inhibiting means preferably comprises a stop member for engaging part of the base when the body is in the fully tilted position. In the preferred embodiment the stop member is arranged to engage a flange of a first interlocking member of the base to inhibit movement of the body relative to the base beyond the fully tilted position. The stop member may be provided by part of the side wall of the body which surrounds the outer periphery of the plate. 
     The base preferably comprises control means for controlling the fan assembly. For safety reasons and ease of use, it can be advantageous to locate control elements away from the tiltable body so that the control functions, such as, for example, oscillation, lighting or activation of a speed setting, are not activated during a tilt operation. 
     The interior passage and the at least one air outlet of the fan assembly are preferably defined by a nozzle mounted on or connected to the body. The base and the body thus may together provide a stand upon which the nozzle is mounted. The at least one air outlet may be located at or towards the front end of the nozzle. Alternatively, the at least one air outlet may be located towards the rear end of the nozzle. The nozzle may comprise a single air outlet or a plurality of air outlets. In one example, the nozzle comprises a single, annular air outlet extending about the opening, and this air outlet may be circular in shape, or otherwise have a shape which matches the shape of the front end of the nozzle. The interior passage preferably comprises a first section and a second section each for receiving a respective portion of an air flow entering the interior passage, and for conveying the portions of the air flow in opposite angular directions about the opening. Each section of the interior passage may comprise a respective air outlet. The nozzle is preferably substantially symmetrical about a plane passing through the centre of the nozzle. For example, the nozzle may have a generally circular, elliptical or “race-track” shape, in which each section of the interior passage comprises a relatively straight section located on a respective side of the bore. Where the nozzle has a race track shape each straight section of the nozzle may comprise a respective air outlet. The, or each, air outlet is preferably in the form of a slot. The slot preferably has a width in the range from 0.5 to 5 mm. 
     In a second aspect the present invention provides a stand for a fan assembly, the stand comprising a base; a body mounted on the base for movement relative thereto between an untilted position and a tilted position, the body comprising at least one air inlet, an impeller, a motor for driving the impeller to draw an air flow through said at least one air inlet, and an air outlet; a brake connected to the base for movement relative thereto; a stop member connected to the base; a section of the body being disposed between the brake and the stop member; and means for urging the brake towards the stop member to urge the section of the body against the stop member to maintain the body in a tilted position relative to the base by means of friction between the section of the body and the stop member. 
     Features described above in connection with the first aspect of the invention are equally applicable to the second aspect of the invention, and vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front perspective view of a fan assembly; 
         FIG. 2  is a front sectional view through the body and the nozzle of the fan assembly; 
         FIG. 3  is a left side sectional view through the body and the nozzle of the fan assembly; 
         FIG. 4( a )  is a left perspective view of the base of the fan assembly, and  FIG. 4( b )  is a right perspective view of the base of the fan assembly; 
         FIG. 5  is a bottom perspective view of the body of the fan assembly; 
         FIG. 6( a )  is a bottom perspective view of a tilt plate of the body, and  FIG. 6( b )  is a close-up of region A identified in  FIG. 6( a ) ; 
         FIG. 7  is a top view of the base of the fan assembly, with the tilt plate attached to the base and in an untilted position relative to the base; 
         FIG. 8( a )  is a front sectional view of the base and the tilt plate taken along line Y-Y in  FIG. 7 , and  FIG. 8( b )  is a close-up of region B identified in  FIG. 8( a ) ; 
         FIG. 9  is a top sectional view taken along line Z-Z in  FIG. 8( a ) ; 
         FIG. 10  is a similar view to  FIG. 9 , but with the tilt plate in a tilted position relative to the base; and 
         FIG. 11( a )  is a side view of the fan assembly with the body in a first fully tilted position relative to the base,  FIG. 11( b )  is a side view of the fan assembly with the body in an untilted position relative to the base, and  FIG. 11( c )  is a side view of the fan assembly with the body in a second fully tilted position relative to the base. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is an external view of a fan assembly  10 . The fan assembly  10  comprises a body  12  having an air inlet  14  in the form of a plurality of apertures formed in the outer casing  16  of the body  12 , and through which a primary air flow is drawn into the body  12  from the external environment. An annular nozzle  18  having an air outlet  20  for emitting the primary air flow from the fan assembly  10  is connected to the upper end of the body  12 . The body  12  is mounted on a base  22  so as to allow the body  12  to tilt relative to the base  22 . The base  22  comprises a user interface for allowing a user to control the operation of the fan assembly  10 . In this embodiment, the user interface comprises a plurality of user-operable buttons  23 ,  24  and a user-operable dial  26 . 
     The nozzle  18  has an annular shape. With reference also to  FIGS. 2 and 3 , the nozzle  18  comprises an outer wall  28  extending about an annular inner wall  30 . In this example, each of the walls  28 ,  30  is formed from a separate component. Each of the walls  28 ,  30  has a front end and a rear end. The rear end of the outer wall  28  curves inwardly towards the rear end of the inner wall  30  to define a rear end of the nozzle  18 . The front end of the inner wall  30  is folded outwardly towards the front end of the outer wall  28  to define a front end of the nozzle  18 . The front end of the outer wall  28  is inserted into a slot located at the front end of the inner wall  30 , and is connected to the inner wall  30  using an adhesive introduced to the slot. 
     The inner wall  30  extends about an axis, or longitudinal axis, X to define a bore, or opening,  32  of the nozzle  18 . The bore  32  has a generally circular cross-section which varies in diameter along the axis X from the rear end of the nozzle  18  to the front end of the nozzle  18 . 
     The inner wall  30  is shaped so that the external surface of the inner wall  30 , that is, the surface that defines the bore  32 , has a number of sections. The external surface of the inner wall  30  has a convex rear section  34 , an outwardly flared frusto-conical front section  36  and a cylindrical section  38  located between the rear section  34  and the front section  36 . 
     The outer wall  28  comprises a base  40  which is connected to an open upper end of the body  12 , and which has an open lower end which provides an air inlet for receiving the primary air flow from the body  12 . The majority of the outer wall  28  is generally cylindrical shape. The outer wall  28  extends about a central axis, or longitudinal axis, Y which is parallel to, but spaced from, the axis X. In other words, the outer wall  28  and the inner wall  30  are eccentric. In this example, the axis X is located above the axis Y, with each of the axes X, Y being located in a plane which extends vertically through the centre of the fan assembly  10 . 
     The rear end of the outer wall  28  is shaped to overlap the rear end of the inner wall  30  to define the air outlet  20  of the nozzle  18  between the inner surface of the outer wall  28  and the outer surface of the inner wall  30 . The air outlet  20  is in the form of a generally circular slot centred on, and extending about, the axis X. The width of the slot is preferably substantially constant about the axis X, and is in the range from 0.5 to 5 mm The overlapping portions of the outer wall  28  and the inner wall  30  are substantially parallel, and are arranged to direct air over the convex rear section  34  of the inner wall  30 , which provides a Coanda surface of the nozzle  18 . A series of angularly spaced spacers may be provided on one of the facing surfaces of the overlapping portions of the outer wall  28  and the inner wall  30  to engage the other facing surface to maintain a regular spacing between these facing surfaces. 
     The outer wall  28  and the inner wall  30  define an interior passage  42  for conveying air to the air outlet  20 . The interior passage  42  extends about the bore  32  of the nozzle  18 . In view of the eccentricity of the walls  28 ,  30  of the nozzle  18 , the cross-sectional area of the interior passage  42  varies about the bore  32 . The interior passage  42  may be considered to comprise first and second curved sections  44 ,  46  which each extend in opposite angular directions about the bore  32 . Each curved section  44 ,  46  of the interior passage  42  has a cross-sectional area which decreases in size about the bore  32 . 
     The body  12  and the base  22  are preferably formed from plastics material. The body  12  and the base  22  preferably have substantially the same external diameter so that the external surface of the body  12  is substantially flush with the external surface of the base  22  when the body  12  is in an untilted position relative to the base  22 . 
     The body  12  comprises the air inlet  14  through which the primary air flow enters the fan assembly  10 . In this embodiment the air inlet  14  comprises an array of apertures formed in the section of the outer casing  16  of the body  12 . Alternatively, the air inlet  14  may comprise one or more grilles or meshes mounted within windows formed in the outer casing  16 . The body  12  is open at the upper end (as illustrated) for connection to the base  40  of the nozzle  18 , and to allow the primary air flow to be conveyed from the body  12  to the nozzle  18 . 
     The body  12  comprises a duct  50  having a first end defining an air inlet  52  of the duct  50  and a second end located opposite to the first end and defining an air outlet  54  of the duct  50 . The duct  50  is aligned within the body  12  so that the longitudinal axis of the duct  50  is collinear with the longitudinal axis of the body  12 , and so that the air inlet  52  is located beneath the air outlet  54 . 
     The duct  50  extends about an impeller  56  for drawing the primary air flow into the body  12  of the fan assembly  10 . The impeller  56  is a mixed flow impeller. The impeller  56  comprises a generally conical hub, a plurality of impeller blades connected to the hub, and a generally frusto-conical shroud connected to the blades so as to surround the hub and the blades. The blades are preferably integral with the hub, which is preferably formed from plastics material. 
     The impeller  56  is connected to a rotary shaft  58  extending outwardly from a motor  60  for driving the impeller  56  to rotate about a rotational axis Z. The rotational axis Z is collinear with the longitudinal axis of the duct  50  and orthogonal to the axes X, Y. In this embodiment, the motor  60  is a DC brushless motor having a speed which is variable in response to user manipulation of the dial  26 . The maximum speed of the motor  60  is preferably in the range from 5,000 to 10,000 rpm. The motor  60  is housed within a motor housing. The outer wall of the duct  50  surrounds the motor housing, which provides an inner wall of the duct  50 . The walls of the duct  50  thus define an annular air flow path which extends through the duct  50 . The motor housing comprises a lower section  62  which supports the motor  60 , and an upper section  64  connected to the lower section  62 . The shaft  58  protrudes through an aperture formed in the lower section  62  of the motor housing to allow the impeller  56  to be connected to the shaft  58 . The motor  60  is inserted into the lower section  66  of the motor housing before the upper section  68  is connected to the lower section  66 . 
     The lower section  62  of the motor housing is generally frusto-conical in shape, and tapers inwardly in a direction extending towards the air inlet  52  of the duct  50 . The hub of the impeller  56  has a conical inner surface which has a similar shape to that of a contiguous part of the outer surface of the lower section  62  of the motor housing. 
     The upper section  64  of the motor housing is generally frusto-conical in shape, and tapers inwardly towards the air outlet  54  of the duct  50 . An annular diffuser  66  is located between the outer wall of the duct  50  and the upper section  64  of the motor housing. The diffuser  66  comprises a plurality of blades  68  for guiding the air flow towards the air outlet  54  of the duct  50 . The shape of the blades  68  is such that the air flow is also straightened as it passes through the diffuser  66 . A cable for conveying electrical power to the motor  60  passes through the outer wall of the duct  50 , the diffuser  66  and the upper section  64  of the motor housing. The upper section  64  of the motor housing is perforated, and the inner surface of the upper section  64  of the motor housing is lined with noise absorbing material  70 , preferably an acoustic foam material, to suppress broadband noise generated during operation of the fan assembly  10 . 
     The impeller housing  68  is mounted on an annular seat  72  located within the body  12 . The seat  72  extends radially inwardly from the inner surface of the outer casing  16  so that an upper surface of the seat  72  is substantially orthogonal to the rotational axis Z of the impeller  56 . An annular seal  74  is located between the impeller housing  68  and the seat  72 . The annular seal  74  is preferably a foam annular seal, and is preferably formed from a closed cell foam material. The annular seal  74  has a lower surface which is in sealing engagement with the upper surface of the seat  72 , and an upper surface which is in sealing engagement with the impeller housing  68 . A plurality of resilient supports are also provided between the impeller housing  68  and the seat  72  for bearing part of the weight of the duct  50 , the impeller  56 , the motor  60 , and the motor housing. The resilient supports are equally spaced from, and equally spaced about, the longitudinal axis of the body  12 . The seat  72  comprises an aperture to enable the cable (not shown) to pass to the motor  60 . The annular seal  74  is shaped to define a recess to accommodate part of the cable. One or more grommets or other sealing members may be provided about the cable to inhibit the leakage of air through the aperture, and between the recess and the internal surface of the outer casing  16 . 
     A guide member  76  is provided about the inlet section  66  and the lower end of the impeller housing  68  for guiding the air flow entering the body  12  towards the air inlet  52  of the duct  50 . The guide member  76  is generally frusto-conical in shape, and tapers inwardly towards the base  56  of the body  12 . The guide member  76  defines in part a tortuous air flow path between the air inlet  14  of the body  12  and the air inlet  52  of the duct  50 , and so serves to block any direct path for noise passing from the air inlet  52  of the duct  50  towards the air inlet  14  of the body  12 . The guide member  76  depends from an annular rib extending about the impeller housing  68 . The outer periphery of the rib may be connected to the inner surface of the body  12 , for example using an adhesive. The outer surface of the guide member  76  which is exposed to the air flow passing through the body  12  is lined with sound-absorbing material  78 . 
     The body  12  comprises a noise suppression cavity  80  located beneath the air inlet  52  of the duct  50 . The cavity  80  is also tuned to the wavelength of the rotational tone of the impeller  56 . The cavity  80  has an inlet  82  which is located beneath the air inlet  52  of the duct  50 , and which is preferably concentric with the air inlet  52  of the duct  50 . A lower wall of the cavity  80  is defined by a curved base  84  of the outer casing  16  of the body  12 . The inlet  82  and an upper wall of the cavity  80  are defined by an annular plate  86  which is connected to the upper peripheral portion of the base  84 . 
     To reduce the level of broadband noise emitted from the fan assembly  10 , an annular sound absorbing member  88  is preferably located between the duct  50  and the cavity  80 . The annular sound absorbing member  88  is concentric with the inlet  82  of the cavity  80 , and has an outer periphery which is in contact with the inner surface of the outer casing  16 . The inner surface of the outer casing  16  is partially lined with sound absorbing material. For example, a sheet of sound-absorbing material  90  may be located immediately downstream of the air inlet  14  to reduce the level of broadband noise emitted through the air inlet  14  of the body  12 . 
     As mentioned above, the body  12  is mounted on a base  22 . With reference to  FIGS. 4( a ) and 4( b ) , the base  22  comprises an upper base member  100  mounted on a lower base member  102 . The upper base member  100  comprises the aforementioned user interface and a control circuit for controlling various functions of the fan assembly  10  in response to operation of the user interface. The upper base member  100  also houses a mechanism for oscillating the upper base member  100  relative to the lower base member  102 . The oscillation mechanism is identified generally at  104  in  FIG. 8( a ) . The operation of the oscillation mechanism  104  is controlled by the control circuit in response to the user&#39;s depression of the button  24  of the user interface. The range of each oscillation cycle of the upper base member  100  relative to the lower base member  102  is preferably between 60° and 120°, and the oscillation mechanism is arranged to perform around 3 to 5 oscillation cycles per minute. A mains power cable (not shown) for supplying electrical power to the fan assembly  10  extends through an aperture formed in the lower base member  102 . 
     The body  12  is mounted on the base  22  so as to be moveable relative to the base  22  between a first fully tilted position, as illustrated in  FIG. 11( a )  and a second fully tilted position, as illustrated in  FIG. 11( c ) . The axes X, Y are preferably inclined by an angle of around 10° as the main body is moved from an untilted position, as illustrated in  FIG. 11( b )  to one of the two fully tilted positions. The outer surfaces of the body  12  and the upper base member  100  are shaped so that adjoining portions of these outer surfaces are substantially flush when the body  12  is in the untilted position. 
     The body  12  is mounted on the base  22  so that the body  12  is slidable relative to the base  22  as it moves to or from a tilted position. Referring again to  FIGS. 4( a ) and 4( b ) , the upper base member  100  comprises a curved upper surface  106 . The curved upper surface  106  is concave in shape, and may be described as generally saddle-shaped. An aperture  108  is formed in the upper surface  106  for receiving an electrical cable extending between the motor  60  and the control circuit. 
     The upper base member  100  comprises a plurality of first interlocking members which each co-operate with a respective second interlocking member located on the body  12  to retain the body  12  on the upper base member  100 . The first interlocking members also serve to guide the movement of the body  12  relative to the upper base member  100  so that there is substantially no twisting or rotation of the body  12  relative to the upper base member  100  as it is moved from or to a tilted position. Each of the first interlocking members extends in the direction of movement of the body  12  relative to the base  22 . In this embodiment, the upper base member  100  comprises two, relatively short, outer interlocking members  110 , and a single, relatively long inner interlocking member  112  located between the outer interlocking members  110 . Each of the outer interlocking members  110  has a cross-section in the form of an inverted L-shape. Each of the outer interlocking members  110  comprises a wall  114  which is connected to, and upstanding from, the upper surface  106  of the upper base member  100 , and a curved flange  116  which connected to, and orthogonal to, the upper end of the wall  114 . The inner interlocking member  112  also has a cross-section in the form of an inverted L-shape. The inner interlocking member  112  comprises a wall  118  which is connected to, and upstanding from, the upper surface  106  of the upper base member  100 , and a curved flange  120  which connected to, and orthogonal to, the upper end of the wall  118 . 
     The body  12  comprises a substantially cylindrical outer casing  16  having an annular lower end  122  and a curved base  84  which is spaced from the lower end  122  of the outer casing  16  to define a recess. The lower surface of the base  84  is convex in shape, and may be described generally as having an inverted saddle-shape. An aperture  124  is formed in the base  84  for allowing the cable to extend into the body  12 . 
     As illustrated in  FIG. 5 , a convex tilt plate  126  is connected to the base  84  of the outer casing  16 . The tilt plate  126  is located within the recess so that the casing  16  surrounds the outer periphery of the tilt plate  126 . The tilt plate  126  has a curvature which is substantially the same as that of the base  84 . The tilt plate  126  has a convex lower surface  128 . The tilt plate  126  is illustrated in isolation from the outer casing  16  in  FIGS. 6( a ) and 6( b ) . The tilt plate  126  comprises a plurality of second interlocking members which are each retained by a respective first interlocking member of the upper base member  100  to connect the body  12  to the base  22 . The tilt plate  126  comprises a plurality of parallel grooves which define a plurality of curved rails of the tilt plate  126 . The grooves define a pair of outer rails  128  and a first inner rail  130 , and these rails  128 ,  130  provide the second interlocking members of the body  12 . Each of the outer rails  128  comprises a flange  132  which extends into a respective groove of the tilt plate  126 , and which has a curvature which is substantially the same as the curvature of the flanges  116  of the upper base member  100 . The first inner rail  130  also comprises a flange  134  which extends into a respective groove of the tilt plate  126 , and which has a curvature which is substantially the same as the curvature of the flange  120  of the upper base member  100 . An aperture (not shown) is formed in the first inner rail  130  for allowing the cable to pass through the tilt plate  126 . The lower surface  128  of the tilt plate  126  comprises a plurality of parallel ridges  136  which extend in the direction of tilting movement of the body  12  relative to the base  22 , and which engage the upper surface  106  of the upper base member  100  when the tilt plate  126  is slid on to the base  22 . This reduces the area of contact between the lower surface  128  of the tilt plate  126  and the upper surface  106  of the upper base member  100 , and so reduces frictional forces between the lower surface  128  of the tilt plate  126  and the upper surface  106  of the upper base member  100  as the body  12  is tilted relative to the base  22 . 
     To connect the body  12  to the upper base member  100 , the tilt plate  126  is inverted from the orientation illustrated in  FIG. 6( a ) . The cable extending through the aperture  124  of the outer casing  16  of the body  12  is fed through the apertures in the tilt plate  126  and the upper base member  100  respectively for subsequent connection to the control circuit within the base  22 . The tilt plate  126  is then slid over the upper base member  100  so that the flange  132  of each outer rail  128  is located beneath a respective flange  116  of the upper base member  100 , and so that the flange  134  of the first inner rail  130  is located beneath the flange  120  of the upper base member  100 .  FIG. 7  is an external view of the base  22  when the tilt plate  126  has been slid fully on to the base  22 . 
     With the tilt plate  126  positioned centrally on the upper base member  100 , the body  12  is lowered on to the tilt plate  126  so that tilt plate  126  is housed within the recess of the outer casing of the body  12 . The upper base member  100  and the body  12  are then inverted, and the body  12  is tilted relative to the base  22  to reveal a first plurality of apertures  140  located on the tilt plate  126 . Each of these apertures  140  is aligned with a respective tubular protrusion  141  (one of which is shown in  FIG. 3 ) on the base  84  of the outer casing  16  of the body  12 . A self-tapping screw is screwed into each of the apertures  140  to enter the underlying protrusion  141 , thereby partially connecting the tilt plate  126  to the body  12 . The body  12  is then tilted in the reverse direction to reveal a second plurality of apertures  142  located on the tilt plate  126 . Each of these apertures  142  is also aligned with a tubular protrusion  143  (one of which is shown in  FIG. 3 ) on the base  84  of the outer casing  16  of the body  12 . A self-tapping screw is screwed into each of the apertures  142  to enter the underlying protrusion  143  to complete the connection of the tilt plate  126  to the body  12 . As the body  12  is tilted relative to the base  22 , engagement between each of the flanges  116 ,  120  of the base  22  with a respective portion of the inner wall of the outer wall  16  which defines the recess in which the tilt plate  126  is located prevents the tilt plate  126  from sliding free from the base  22 . 
     The fan assembly  10  includes a mechanism for retaining the body  12  in a desired tilted position relative to the base  22 . This mechanism will now be described with reference to  FIGS. 4( a ), 4( b ), and 6( a )  to  10 . 
     Referring first to  FIGS. 4( a ) and 4( b ) , the upper base member  100  comprises a brake  150  which is moveable relative to the upper base member  100 . The brake  150  comprises a pair of side arms  152  which each extends over and partially about a respective guide rail  154  formed on the upper base member  100 . The guide rails  154  are parallel, and extend in a direction which is orthogonal both to the walls  114 ,  118 , and to the direction in which the body  12  moves relative to the base  22 . The brake  150  is secured to the guide rails  154  in a snap-fit connection which allows the brake  150  to move along the guide rails  154  in a direction which is parallel to the guide rails  154 . The brake  150  comprises a plurality of brake pads  156 . The pads  156  may be secured to the brake  150 , or they may be integral with the brake  150 . The pads  156  are located on a surface of the brake  150  which faces a side surface  158  of a stop member  160 . In this embodiment, the stop member  160  is in the form of a rail which is connected to, and is preferably integral with, the upper surface  106  of the upper base member  100 . The stop member extends in a direction which is parallel to the walls  114 ,  118  of the upper base member  100 . The brake  150  is urged towards the stop member  160  by a spring  162  or other resilient element. The spring  162  is located between the brake  150  and a seat  164  connected to, and preferably integral with, the upper surface  106  of the upper base member  100 . 
     With reference to  FIGS. 8( a ), 8( b )  and  FIGS. 9 and 10 , as the tilt plate  126  is slid on to the upper base member  100  a section of the tilt plate  126  slides between the brake  150  and the stop member  160 . In this embodiment, a second inner rail  166  of the tilt plate  126  slides between the brake  150  and the stop member  160 . The second inner rail  166  also extends in the direction of the tilting movement of the body  12  relative to the base  22 , and has a first side surface  168  and a second side surface  170  which is parallel to the first side surface  168 . The pads  156  of the brake  150  engage the first side surface  168  of the second inner rail  166 , which causes the second side surface  170  to be pushed against the side surface  158  of the stop member  160 .  FIG. 10  illustrates the relative positions of the base  22  and the tilt plate  126  when the body  12  is in a tilted position relative to the base  22 . The spring constant of the spring  162  is selected such that the friction forces generated between the side surface  158  of the stop member  160  and the second side surface  170  of the second inner rail  166  as the brake  150  urges, under the force of the spring  162 , these surfaces together is sufficient to hold the body  12  in a tilted position relative to the base  22  against the action of the weight of the body  12  and the nozzle  18  connected to the body  12 . 
     Returning to  FIGS. 6( a ) and 6( b ) , a recess  172  is provided on the first side surface  168  of the second inner rail  166 . The recess  172  is shaped to accommodate at least the part of the brake pads  156  of the brake  150 . In the tilted position of the tilt plate  126 , and therefore the body  12 , relative to the base  22  which is illustrated in  FIG. 10 , the brake pads  156  are spaced from the recess  172 . As the tilt plate  126 , and therefore the body  12 , moves towards the untilted position illustrated in  FIG. 9 , the brake pads  156  slide along the first side surface  168  of the second inner rail  166 . The decrease in the force required to move the body  12  relative to the base  22  as the brake pads  156  enter the recess  172  can allow the user to identify that the body  12  has been moved to its untilted position. 
     To operate the fan assembly  10  the user presses button  23  of the user interface, in response to which the control circuit in the base  22  activates the motor  60  to rotate the impeller  56 . The rotation of the impeller  56  causes a primary air flow to be drawn into the body  12  through the air inlet  14 . The user may control the speed of the motor  60 , and therefore the rate at which air is drawn into the body  12  through the air inlet  14 , by manipulating the dial  26 . The rotation of the impeller  56  causes a primary air flow to enter the body  12  through the air inlet  14 , and to pass to the air inlet  52  of the duct  50 . The air flow passes through the duct  50  and is guided by the shaped peripheral surface of the air outlet  54  of the duct  50  into the interior passage  42  of the nozzle  18 . Within the interior passage  42 , the primary air flow is divided into two air streams which pass in opposite angular directions around the bore  32  of the nozzle  18 , each within a respective section  44 ,  46  of the interior passage  42 . As the air streams pass through the interior passage  42 , air is emitted through the air outlet  20 . The emission of the primary air flow from the air outlet  20  causes a secondary air flow to be generated by the entrainment of air from the external environment, specifically from the region around the nozzle  18 . This secondary air flow combines with the primary air flow to produce a combined, or total, air flow, or air current, projected forward from the nozzle  18 .