Abstract:
A mounting assembly for a ceiling fan, adapted to attach a rotating fan blade assembly to a ceiling suspension and electric motor assembly, said electric motor assembly including an electrical rotor and an electrical stator, said stator being horizontally disposed within said rotor and connected to said rotor via a double row angular ball bearing.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to the field of the mechanical design of electrically operated ceiling fans. In particular it relates to an improved assembly and method for assembling the fan rotor and stator. 
       BACKGROUND OF THE INVENTION 
       [0002]    Ceiling fans are conventionally constructed using one of two motor types: type (A) where a central shaft is attached to a stator, where said shaft is stationary while the blades are attached to a rotor which rotates about the periphery of the stator, or; type (B) where the central shaft is attached to the rotor with the blades attached thereto and said shaft rotates with both rotor and shaft surrounded or encompassed by the stator. 
         [0003]    Fan motors of the type (A), where the rotor rotates around the periphery of the stator, require the rotor to be held in a fixed longitudinal and lateral position relative to the shaft and the stator. Typically this is achieved by the use of two bearings and two motor housings containing said bearings, these housings being made of resilient material such as sheet metal and of a thickness that yields a small amount of elastic deformation thus allowing them to be pressed around or otherwise attached to the rotor. The rotor is thus prevented from rectilinear motion but is allowed curvilinear motion. ‘Steps’ on the shaft allow correct longitudinal positioning of the bearings. The blades of the ceiling fan may be attached to the rotor by various means. The stationary body of the fan (if any), suspension mechanism, light fittings and trimmings may also be attached to the stationary shaft where it projects from the bearings by various means. Motors of this type are typically split-capacitor induction motors. 
         [0004]    Fan motors of the type (B), where the stator is fixed around the periphery of the rotor and the rotor and shaft rotate within the stator, require the rotating shaft to be held in a fixed longitudinal and lateral position relative to the stator and any devices attached to it. Typically two bearings, or one bearing plus a bushing, are pressed into the stator, or housing made of resilient material such as sheet metal and of a thickness that yields a small amount of elastic deformation thus allowing it to be pressed around or otherwise attached to the stator. Steps on the shaft may allow correct longitudinal positioning of the bearings. The rotor and shaft is thus prevented from rectilinear motion but allowed curvilinear motion. The blades of the ceiling fan may be attached to the shaft by various means. The stationary body of the fan (if any), suspension mechanism, light fittings and trimmings may also be attached to the stator by various means. Motors of this type are typically split-capacitor or shaded-pole induction motors or brushless DC motors. 
         [0005]    Electric motors of most types in general, when used for this purpose, require the rotor to be stabilised laterally so the electromotive forces generated between stator windings and rotor windings is translated into curvilinear motion and do not result in the rotor being pulled sideways and into contact with the stator. This is usually achieved by the bearings being spaced a suitable distance apart and the material housing the bearings being suitably resilient either by nature of the materials themselves or forces imposed by mechanical design. 
         [0006]    For motors of the type (A) or (B), when used with ceiling fans, the bearings or combination of bearings and bushes add considerable height and bulk to the motor assembly, before taking into account the attachment of blades and the stationary body of the fan (if any), suspension mechanism, light fittings and trimmings. The height of the motor assemblies described as types (A) and (B) prevents conventional ceiling fans from adopting slim or thin body profiles. 
         [0007]    The attachment mechanism residing between the body of the ceiling fan and the suspension mechanism requires attachment to the stationary shaft (as per type (A)) or to the stator (as per type (B)) and in either case adequate clearance must be provided from rotating parts, which again increases the height required by the body of the fan. This further restricts the minimum profile achievable with motors of these designs. 
         [0008]    Accordingly, it is an object of the invention to provide a bearing assembly for a ceiling mounted fan that facilitates a slimmer or flatter design of a fan hub. 
       SUMMARY OF THE INVENTION 
       [0009]    According to one aspect of the invention, there is provided a mounting assembly for a ceiling fan, adapted to attach a rotating fan blade assembly to a ceiling suspension and electric motor assembly, said electric motor assembly including an electrical rotor and an electrical stator, said stator being horizontally disposed within said rotor and connected to said rotor via a bearing. Prefrably, the bearing is a double row angular contact ball bearing. 
         [0010]    Preferably, said bearing is retained within the rotating components of the fan body, and most preferably the stator is adapted to at least partially receive said bearing within its profile. For example, this may be achieved by recessing the bearing carrier assembly into a pocket within the stator. This further enhances the ability of the fan designer to produce operational fans having a low, slim or thin design. 
         [0011]    In the background discussion above, there are described some limitations on decreasing the profile height of a ceiling fan motor assembly due to the attachment mechanism having to be located above rotating parts on motors, as per (A) and (B). The present invention, including an attachment mechanism that is directly connected to non-rotating parts, lowers the profile height not by the method of attachment of said mechanism but by the removal of the bearing carrier conventionally located above the stator. The present invention allows the bearing carrier to be placed within the rotating parts only, and preferably locates it in a recess below the stator. 
         [0012]    One further advantage of this ‘gained’ space is that it facilitates the addition of motor covers made from insulating materials, thus allowing the user, or other untrained personnel to safely access these areas without risk of damage to electrical components and motor windings. 
         [0013]    According to another aspect of the invention, there is provided a ceiling fan having a low-profile central hub, incorporating a mounting assembly as defined above. 
         [0014]    According to another aspect of the invention, there is provided a method of construction of a mounting assembly for a ceiling fan. 
         [0015]    Now will be described, by way of a particular, non-limiting example, a preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0016]      FIG. 1  is an exploded partial view of a ceiling fan assembly in accordance with the invention. 
           [0017]      FIG. 2  is a detailed view of the assembly in  FIG. 1 . 
           [0018]      FIG. 3  is a sectional view of part of a ceiling fan assembly in accordance with the invention. 
           [0019]      FIG. 4  is a sectional view of a fully assembled ceiling fan assembly in accordance with the invention. 
           [0020]      FIG. 5  is a detailed view of the assembly in  FIG. 4 . 
           [0021]      FIG. 6  is a top view of a part of the assembly of  FIG. 4 . 
           [0022]      FIG. 7  is a detailed view of the assembly of  FIG. 6 . 
           [0023]      FIG. 8  is an exploded isometric view of a top cover assembly of the ceiling fan assembly of  FIG. 4 . 
           [0024]      FIG. 9  is an alternative exploded isometric view of a top cover assembly as per  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Now will be described the invention as discussed above, and the method of assembling a ceiling fan using a single bearing to allow slim, thin and low profile designs that are not achievable with conventional assemblies. 
         [0026]    With reference to  FIG. 1 , the stator  20  is fabricated using laminated silicon steel in the conventional manner, but with a recess  21  incorporated into the lower surface of said stator  20 . During assembly, the stator  20  is pressed over the motor shaft  25  until reaching a step  26  in the shaft. A flat  27  machined onto the round section of the shaft  25  aligns with a matching flat section  28  of the shaft hole in the stator  20 . This orients the shaft and stator in a fixed position relative to one another and thus the wire entry/exit holes  29  in the shaft are aligned with the start and stop position of the stator windings. 
         [0027]    The use of a single double-row angular-contact ball bearing  10  in construction of the ceiling fan is a key to the invention. Particular advantages are derived from locating the bearing  10  in a recess  21  within the stator  20  so the force couple that acts laterally on the bearing  10  is greatly reduced, preferably to a magnitude less than that which would typically be generated by a bearing located further from the centre of the stator  20 , thereby overcoming the need to use two bearings located distant from the centre of the stator (typically above and below the stator, as per the prior art). The selection and use of a double row angular contact ball bearing  10  allows a single bearing to provide sufficient lateral load capacity to cope with rectilinear electromagnetic forces operating between stator windings and rotor windings. 
         [0028]    In construction of a fan according to the invention, a single double-row angular contact ball bearing  10  (for example the NACHI 5202-2NS, as supplied in Australia by Nachi (Australia) Pty Ltd, of Unit 1, 23-29 South Street, Rydalmere, N.S.W. 2116), is pressed onto the motor shaft  25  until reaching a step  26  in the shaft. As shown in  FIGS. 2 and 3 , a circlip  15  snaps into a groove  70  to provide positive retention of the bearing  10  on the shaft  25 . 
         [0029]    The stator-shaft-bearing-circlip sub-assembly as detailed in  FIG. 2  is then pressed into the central band  5  and positively retained in place by points of material displacement (pinch point) as shown in  FIGS. 4 and 5  or with screws  85  impinging on the top edge of the outer shell of the bearing  95 . Access to the pinch points  80  and/or retaining screws  85  is made via holes  90  placed in the stator  20  for this purpose. The same access holes may also be used during previous processes for positioning and rotating the stator during coil winding. 
         [0030]    The stator  20  is positioned within the ring-shaped rotor  22 . The rotor  22  is operably connected to the central band  5 . The central band  5  features slots  6  designed to receive removable blades. 
         [0031]    Mechanical integrity and retention of rotating parts is assured since the bearing  10  cannot be displaced from the stationary shaft  25  due to the circlip  15  and groove  70 . The central band  5  cannot be displaced from the bearing  10  due to the pinch points  80  and screws  85  as shown in  FIG. 6 . 
         [0032]    With reference to  FIGS. 4 and 5 , a ceiling fan according to the invention places the bearing carrier  75  within the central band  5  and locates it in a recess  21  located in the bottom surface of the stator  20  (detailed in  FIG. 5 ), thus avoiding the need to provide space for rotating parts or bearing carrier assemblies above said stator. 
         [0033]    Electrical insulation and physical separation between stator coils and metallic parts of the central band  5  is provided by the bottom stator insulation cover  60  and the top stator insulation cover  40 . A rotor cover  61  is also provided. 
         [0034]    The top stator insulation cover  40  is retained by the cover screws  100  which have a head  101  with cross-section resembling a capital letter ‘I’. The lower horizontal part of the ‘I-shaped’ head  101  presses onto the top surface of the top insulation cover  40  retaining it in position. 
         [0035]    The ceiling fan motor and blade assembly is suspended from the ceiling by a rigid tube  65  conventionally referred to as a “down rod”. A wave washer  45  slides over the motor shaft and rests within a recess formed in the top insulation cover  40 , shown in  FIGS. 8 and 9 . The top of the motor shaft  25  is threaded and the lower end of the down rod tube  65  is threaded to match. The down rod is screwed onto the motor shaft and compresses the wave washer  45 . 
         [0036]    The down rod  65  is screwed onto the motor shaft  25  until the wave washer  45  is sufficiently compressed, and holes  29  drilled into the motor shaft  25  and down rod  65  align. The wave washer  45  prevents play in the join between shaft and down rod and thus eliminates knocking and other noises. A locking pin  55  is inserted in the holes  29  to additionally support the weight of the fan motor assembly and to provide an anti-torque device. This helps to prevent reactive motion from unscrewing or loosening the down rod, when starting the fan. The holes align, and the locking pin is able to pass therethrough, only when sufficient compressive force is exerted on the wave washer  45 . 
         [0037]    The locking pin  55  is tethered to the top insulation cover  40  so it cannot be misplaced. The tether is only of sufficient length to allow the pin  55  to be inserted into the holes  29  in the down rod  65  and motor shaft  25 . The thickness of the head of the locking pin is greater than the clearance distance between the top insulation cover  40  and the top cover  150  so unless the pin is inserted into the proper position (where adequate clearance exists) it is not possible for the user to install the top cover  150  due to obstruction by the tethered pin. The tether itself is not thick enough to cause obstruction. This provides an added safety feature. 
         [0038]    The upper horizontal part  102  of the I-shaped head  101  of the cover screws  100  mate with a keyway ring  105 , as per  FIG. 9 , fitted within the top cover  150  and used to secure the top cover in place. The top cover  150  is secured by rotating the cover approximately 30 degrees, so the narrower sections of the individual key-way slots  106  are engaged. The top cover  150  is removable and re-attachable by the user to install and/or remove the ceiling fan blades during installation or maintenance. 
         [0039]    It will be appreciated by persons skilled in the art that the above described embodiments are not the only ways in which the invention can be put into practice. There are other alternative embodiments which, while different in some details, nevertheless fall within the scope of the invention.