Abstract:
A fan blade comprising a mount supporting a plurality of superimposed fan blade segments arranged to slide relative to one another from a retracted storage configuration to an extended operative configuration.

Description:
[0001]    This invention relates to a ceiling fan and more particularly relates to a ceiling fan with retractable blades. 
       BACKGROUND OF THE INVENTION 
       [0002]    The problem with many ceiling fans is that the radially projecting blades become unsightly dust collectors when the fan is not in use. Ceiling fans that often incorporate light fittings and it has been proposed to incorporate retractable blades that retract within the confines of the light fitting when not in use and expand radially outwardly when in use to operate as conventional fan blades. 
         [0003]    Problems with fans of this kind concern ensuring a balanced configuration especially as the blades move between the retracted and operative positions. A further problem with fans of this kind is the limit on the length of the blades to enable then to retract within the confines of the light fitting. This usually requires the blades to nest with the tip of one blade above the root of the adjacent blade, thus leading to an unsightly slack of blades. If the blades are made shorter to reduce the need for overlapping then the blades lack the aerodynamics to move sufficient air to operate efficiently as a fan. 
         [0004]    It is these issues that have brought about the present invention. 
       SUMMARY OF THE INVENTION 
       [0005]    According to one aspect of the present invention there is provided a fan blade comprising a mount supporting a plurality of superimposed fan blade segments arranged to slide relative to one another from a retracted storage configuration to an extended operative configuration. 
         [0006]    According to another aspect of the present invention there is provided a ceiling fan comprising an electric motor adapted to drive a rotating plate that supports a plurality of equally spaced fan blades that extend radially of the plate, each fan blade comprising a root and a tip joined by leading and trailing edges, the root being adapted to be secured to the plate, wherein each blade comprises a plurality of fan blade segments arranged to slide telescopically one within the other whereby the fan blade segments can be located substantially within the periphery of the plate in a retracted configuration and can extend radially outwardly in an operative configuration. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: 
           [0008]      FIGS. 1   a ,  1   b  and  1   c  are respectively plan, side and perspective views of a fan in an expanded operative configuration, 
           [0009]      FIGS. 2   a ,  2   b , and  2   c  are respectively plan, side and perspective views of the fan in a retracted inoperative configuration, 
           [0010]      FIGS. 3   a  and  3   b  are respectively plan and side elevational views of the fan in the retracted configuration illustrating a drive assembly, 
           [0011]      FIGS. 4   a ,  4   b  and  4   c  are respectively plan, side and perspective views of the fan in the expanded operative configuration with components omitted for clarity, 
           [0012]      FIG. 5  is a plan view of part of components for the fan in the expanded configuration, 
           [0013]      FIG. 6  is a plan view of one blade assembly in the expanded configuration, 
           [0014]      FIG. 7  is a cross sectional view taken along the lines A-A of  FIG. 6 , 
           [0015]      FIG. 8  is a cross sectional view taken along the lines B-B of  FIG. 6 , and 
           [0016]      FIG. 9  is a cross sectional view taken along the lines C-C of  FIG. 6 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The ceiling fan  10  as illustrated in the accompanying drawings comprises an electric motor  11  that is hung from the ceiling. The electric motor  11  is coupled to a circular plate  12  whereby the motor  11  rotates the plate  12  about a vertical axis. The plate  12  is adapted to support four equally spaced fan blade assemblies  20 ,  21 ,  22 ,  23 . Each blade assembly  20  to  23  comprises three fan blade segments  30 ,  31 ,  32  that can slide relative to one another from a retracted position ( FIG. 2 ) where the fan blade segments are within the confines of the plate  12  to an outward operative position ( FIG. 1 ) in which the fan blade segments  30 - 32  project radially outwardly of the plate  12  to facilitate movement of air as the plate  12  is rotated by the electric motor  11 . It is understood that the electric motor  11  can be either on top of or below the plate  12 . 
         [0018]    Each blade assembly  20 - 23  is positioned on the periphery of the plate  12  via a mount  40  that is secured to the plate  12 . As shown in  FIG. 2   a  the mounts  40  are equally spaced around the periphery of the plate to be diametrically opposed to one another. 
         [0019]    In this embodiment the blade comprises three blade segments, namely the first outer segment  30 , an intermediate segment  31  that is telescopically mounted within the outer segment  30 , and an inner blade tip  32  that is again telescopically mounted within the intermediate section. 
         [0020]    Each mount  40  comprises a pair of support legs  41 ,  42  having outwardly extending flanges  43 ,  44  that enable the legs to be screwed to the surface of the plate  12 . The support legs  41 ,  42  support a bridging member  45  that defines a slot  46  that accommodates a first outer blade segment  30 . The slot defines a passageway that allows the blade segments  30  to be a smooth sliding fit within the slot  46 . The legs  41 ,  42  of the mount assembly are also arranged so that the slot is on an incline of between 10 and 15 degrees (see  FIG. 2   b ). The angle on the slot gives the blade, which is otherwise flat, an angle of incidence to give the desired air movement when in the extended and operative position. 
         [0021]    The blade segments  30 ,  31 ,  32  all slide relative to one another so that in the retracted position ( FIG. 2 ) the tip  32  is wholly within the intermediate segment  31  which is wholly within the outer segment  30 . In the extended position shown in  FIG. 2  the tip  32  projects radially outwardly of the intermediate segment  31  which is in turn radially outwardly of the outer segment  30 . The telescopic arrangement of the three blade segments allows the segments to slide outwardly and the force to urge this outward movement is the centrifugal force generated by rotation of the plate  12  by the electric motor  11 . 
         [0022]    Each diametrically opposed pair of blade assemblies  21 ,  22  or  23 ,  24  are interconnected by a chain  50  that rotates about a sprocket  51  located on the underside of each mount  40 . The chain is also coupled to a centrally located sprocket  52  that is in turn coupled to a coil spring  53  located within a housing  54 . The chain  50  is attached to an elongate rod  60  via an adjustable linkage. 
         [0023]    As shown in  FIG. 6  the rod  60  extends parallel to the chain  50  and is coupled to an inner end of the outer blade segment  32 . Movement of the chain  50  pills the rod  60  radially inwards to pull the outer blade segment  32  into the intermediate segment  31  until the inner end of the blade segment  32  abuts stop  63  on the inner end of the intermediate segment  31 . Further movement of the rod  60  causes inward displacement of the intermediate segment  31  until it engages stops  64  on the inner end of the first blade segment  30 . Al these segments  30 ,  31 ,  32  are then pulled by the rod  60  under the mount  40  to assume the fully retracted position shown in  FIG. 2 . 
         [0024]    As the centrifugal force of the fan  10  forces the blade  30 - 32  segments outwardly the movement of the segments causes rotation of the sprocket  51  under the mount  40  to drive the chain  50  to in turn rotate the central sprocket  52  against the spring  53 . As the fan  10  slows down the coil spring  53  urges the central sprocket  52  to rotate the chain  50  and pull back the fan segments  30 - 32  to the retracted position. In this manner, the sprocket and chain drive not only controls the outward movement of the fan segments but through the spring  53  brings the segments back into the retracted position when not in use. To avoid collision of the chains  50  two central sprockets  52  are provided in different vertical planes with the upper sprocket driving the fan blade assemblies  20  and  21  and the lower sprocket driving the other pair of fan blade assemblies  22  and  23 . 
         [0025]    The fan blade segments  30 - 32  are moulded in plastics to define leading and trailing edges. The blade segments  30 - 32  are substantially flat and the tip segment  32  has a curved end. 
         [0026]    The fan described above has a number of advantages over conventional fans with retractable blades. Because the blades do not pivot from the operative to the retracted positions there is no danger of collision between the blades during the retraction process. Furthermore, the fact that the blade segments expand radially or in a longitudinal sense means that the blades can be designed to have increased length to thereby increase the airflow. Furthermore, the telescopic location of the blade segments allows the fan to assume a compact and comparatively thin configuration in the retracted position which makes the fan, especially when it incorporates a light fitting, much more attractive in the retracted position than is the case with other fans with retractable blades where the blades form an unsightly nest above the light fitting. 
         [0027]    In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.