Abstract:
This invention relates to electric fans or blowers which may be used in, for instance, domestic, medical, commercial, industrial and transport applications.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to electric fans or blowers which may be used in, for instance, domestic, medical, commercial, industrial and transport applications.  
         [0002]     Reference will be made hereinbelow to ventilating fans for causing air to be expelled from a space, for instance, from a kitchen. Such fans may be wall, window or duct mounted so that the air is expelled from the kitchen or other space to the exterior of the building. However, it should be appreciated that the present invention may be embodied in all sorts of different pressure and suction fans and blowers and, more generally, to fluid moving devices, for example circulation devices, in which the fluid is a gas or a liquid.  
       BACKGROUND TO THE INVENTION  
       [0003]     Ventilating fans are known which may be of the centrifugal or axial variety. In general, they are rather inefficient devices and there is a need for a ventilating fan which can effectively shift large volumes of air with low electric power requirements. Existing fans have components such as a motor, electronics and connectors, that, because they are positioned in the path of air passing through the fan, are vulnerable to dust, grease and other contaminants. These contaminants cause reduction in life expectancy of the components and make them difficult to clean.  
         [0004]     An attempt to deal with these problems involves the provision of some form of device to pre-filter the air and such a device adds to the cost of the fan and itself has maintenance requirements.  
         [0005]     Accordingly, there is a need for a ventilating fan which can be easily disassembled, at least to the extent that its front cover may be removed to allow the consequential easy removal of the various moving parts, for instance, the impeller. Once these moving parts are removed, smooth, rounded internal surfaces are more easily cleaned.  
       STATEMENTS OF THE INVENTION  
       [0006]     According to the present invention there is provided an electric fan comprising a housing body, a front cover defining a fluid inlet to the housing and a rear fluid outlet aligned with said fluid inlet, a motor and an impeller mounted within the housing between said inlet and outlet for drawing fluid into the housing in a direction from said inlet towards said outlet in an outwardly radially direction before exiting via the outlet, the front cover being moveable relative to the housing to allow access to said impeller and motor.  
         [0007]     The fact that the front cover is moveable relative to the housing body enables easy access to the components of the fan for servicing and cleaning purposes. The front cover may, for example, be hinged to a wall of the housing body.  
         [0008]     In a more preferred embodiment of the invention the front cover is removable. For example, the front cover is attached to the housing by screws or a snap fit-mechanism or is slidable relative to the housing body. Even more preferably the front cover clips onto the housing body about their peripheral edges.  
         [0009]     In order to increase the safety aspect of the fan the movement of the front cover effects isolation of the motor and thus ensures that it is not possible to run the electric fan in an unguarded state.  
         [0010]     Once the front cover has been moved or removed to allow access to other components within the fan, such as the impeller, hub, motor mount, air collector, driver or duct adapter, these components can be simply cleaned in situ using an appropriate cleaning solution, for example warm soapy water.  
         [0011]     In an even more preferred embodiment of the invention the impeller is removable from the electric fan and can be thoroughly cleaned by immersion in an appropriate cleaning solution, for example water soapy water. This avoids the problem of unsightly fans with clogged filters. Preferably the impeller is removable from the housing by relative movement along the axis between the fluid inlet and the fluid outlet.  
         [0012]     Any un-removable components exposed within the fan by the removal of the front cover and/or impeller are preferably designed and arranged such that plain surfaces are exposed allowing easy cleaning with, for instance, a damp cloth. Furthermore such components, for example, the motor, the drive and the controls, are preferably sealed from dust and water spray, which makes them not only easy to clean but also both hygienic and safe. Accordingly, a fan of the present invention may have all those components which are vulnerable to contamination by dust, grease and other contaminants, encased in protective chambers, thereby avoiding the problems mentioned above in connection with existing electric fans. Cleaning is fundamentally easier and quicker and life expectancy is extended. Furthermore, the requirement for a device to pre-filter the air is eliminated.  
         [0013]     In a further preferred embodiment of the invention the components of the fan are co-axially arranged along an axis extending between the fluid inlet and the fluid outlet such that removal of a first component by movement along the axis facilitates access to a second component. For example, removal of the front cover enables access to the impeller, removal of the impeller enables access to the motor mount, removal of the motor mount enables access to the motor and so on.  
         [0014]     In an alternative embodiment of the invention the components of the electric fan are concentrically arranged along the axis.  
         [0015]     In a still further preferred embodiment of the invention which further includes a means to collect the radially directed fluid and direct it towards the fluid outlet, the collecting means being a plurality of collection chambers.  
         [0016]     Preferably the collection chambers are circumferentially spaced about said axis. Preferably, the collecting means is a plurality of helical conduits, each having a circumferentially disposed inlet and axially disposed outlet.  
         [0017]     The provision of multiple collecting chambers to receive air from a rotating impeller allows significant reductions in space for a given performance, and without reduction in efficiency, compared with a conventional fan.  
         [0018]     In a preferred embodiment of the present invention, the fan is provided with a humidity sensor and means for automatically increasing the speed of the fan in response to a predetermined increase in the humidity of the fluid passing through the fan.  
         [0019]     The inclusion of a humidity sensor in a fan of the present invention allows the fan to be responsive very rapidly to a situation requiring effective operation of the fan. Such situations may include the running of a bath or shower in a bathroom or the cooking of a meal in a kitchen. The fan can be running at a relatively low speed (standby operation) with a very small flow rate passing through it. As and when the humidity sensor detects a sufficient increase in the humidity of the air passing through the fan, the speed of the fan may be automatically increased. In this way the fan will be “in control” of the local environment at all times. As soon as any increase in local humidity is dealt with, the fan will quickly and automatically revert to standby mode.  
         [0020]     If the “non-local” environment is itself both warm and humid, the above described system, incorporating a humidity sensor, would result in the fan continuing to operate at an increased flow rate. To deal with the situation, an “outside” humidity sensor can also be installed along with appropriate circuitry to compare humidity both “locally” and “non-locally”.  
         [0021]     A fan in accordance with the present invention may be one which can operate at two speeds, a low speed or trickle mode and a higher speed or boost mode. When fitted with a humidity sensor as described above, the fan may be provided with a variable speed function to match the rising or falling humidity. The above described fans are provided with a housing body or rear car case which is an easy to fit, maintenance-free item which never needs to be removed from the wall to which it is secured. A fan in accordance with the present invention may be small enough for bathroom installations but with more than enough power for kitchens. Small power consumption is achieved through the use of a self-regulating, whisper-quiet, DC electronically commutated motor. The fan is filterless. The internal design gives air management which forces dust and contaminates away from the sealed electric motor, pushing it past internal smooth surfaces to the atmosphere, thereby avoiding the need for a filter. As the motor is protected from noise-inducing, power-draining dirt and grime, it remains quiet, efficient and economical throughout its life.  
         [0022]     At the heart of the fan is located the above described helical power expansion chamber which moves large volumes of vapour-laden and/or contaminated air, all within the confines of a small piece of equipment operating with great power efficiency.  
         [0023]     It will be understood that the electric fan of the present invention can be an extract fan, pressure device or circulation device. Preferably the fluid is air.  
         [0024]     In an alternative embodiment of the invention the electric fan is a pump for a liquid.  
         [0025]     There is also provided a fan assembly comprising two or more electric fans according the invention wherein the fans are mounted within a common housing.  
         [0026]     There is also provided an appliance comprising an electric fan according to the invention, for example a domestic appliance. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The invention is illustrated, by way of example only, by the embodiments shown in the accompanying drawings, in which:  
         [0028]      FIG. 1  is a front view of an electric fan in accordance with the present invention;  
         [0029]      FIG. 2  is a side view of the electric fan of  FIG. 1 ;  
         [0030]      FIG. 3  is a section on line AA of  FIG. 1 ;  
         [0031]      FIG. 4  is a section on line BB of  FIG. 1 ;  
         [0032]      FIG. 5  is a rear view of the fan of  FIG. 1 ;  
         [0033]      FIG. 6  is an exploded perspective view of the fan of  FIG. 1 ; and  
         [0034]      FIG. 7  is a scrap assembly showing part of an electric fan similar to that of  FIG. 1  and incorporating a humidity sensor. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     The invention will now be described, by way of example, with reference to the accompanying drawings.  
         [0036]     An electric fan  1  is broadly rectangular when viewed from the front or the rear as shown in  FIGS. 1 and 5 . From the side it is again generally rectangular although with a somewhat protruding front face  3  and a rear extension  5  provided by a duct adaptor  7 .  
         [0037]     The main components of fan  1  are perhaps best illustrated in the exploded view of  FIG. 6 , these components being front cover  9 , impeller  11 , hub  13 , motor mount  15 , motor  17 , air collector  19 , housing body  21  and the above mentioned duct adaptor  7 . These components are all connected together essentially concentrically along an axis extending between the front cover  9  and the duct adaptor  7 .  
         [0038]     Front cover  9  includes a centrally disposed circular air inlet which itself has a central hub  25  surrounded by concentric rings  27 , interlinked by generally radial webs  29 .  
         [0039]     Front cover  9  clips on to housing body  21  about their respective peripheral edges. Housing body  21  is in the form of a deep, generally rectangular wall  31  which is partly open at both ends, the front end being for securing to front cover  9  and the rear end for securing to duct adaptor  7 . Within walls  31 , air collector  19  is provided with a lead cover  5  which encloses the electric leads.  
         [0040]     Together the front cover  9  and housing body  21  provide the overall housing for the electric fan  1 . Within the housing the various components  11 ,  13 ,  15 ,  17  and  19  are located and extending rearwardly from the housing is the duct adaptor  7 .  
         [0041]     Considering the components within the housing from front to rear, impeller  11  has a central hub connector  33  which includes a fastening device for securing the impeller to adjacent hub  13 . This fastening device (not shown) is released by gripping radially outwardly biased lugs  35  and pressing inwardly towards the centre of the hub connector  33 .  
         [0042]     Surrounding hub connector  33  are axially spaced apart forward and rearward rings  37  and  39 . Between these rings extend peripherally spaced apart vanes  41 , each vane being attached at each end to a respective ring  37 ,  39  and extending generally towards the centre of the impeller. Each vane  41  is broadly an elongate rectangle being curved across its width.  
         [0043]     Hub  13  is generally of truncated dome shape having a flattened forward end  43  from the middle of which projects a circular peg  45 . On opposite sides of peg  45  are apertures  47  and these, together with peg  45 , are for engagement with corresponding elements (not shown) of the fastening device located within the central hub connector  33  of impeller  11 .  
         [0044]     The inner surface of rearward rim  49  and forward circular flange  51  of motor mount  15  form a labyrinth seal between the moving and stationary components of the fan.  
         [0045]     Motor mount  15  is in the form of a cup within which is located the forward end of motor  17 . Motor  17  is provided with a forwardly extending stub shaft  53  which extends through motor mount  15  to locate in the hollow peg  45  as best illustrated in  FIG. 4 . When the motor is running, stub shaft  53  rotates and this in turn causes hub  3  and impeller  11  to rotate.  
         [0046]     The rotation of impeller  11  causes air to be sucked into the housing of fan  1  through the inlet provided in front cover  9 . Surrounding the above described components  11 ,  13 ,  15  and  17  is an inner housing in the form of an air collector  19 . In this embodiment, collector  19  comprises two air collection ducts/conduits  55   a  and  55   b  ( 55   b  is not shown) each of which are substantially helically shaped channels which extend both circumferentially and rearwardly from the front of the collector  19  towards its rear. The orientation of the helical channel of air collection duct  55   a  is such that it directs air in a clockwise direction towards a peripherally located discharge  57   a  at the rear. The orientation of the helical channel of air collection duct  55   b  is such that it directs air in an anti-clockwise direction towards a peripherally located discharge  57   b  (not shown) at the rear. This air collector  19  accordingly directs air thrown radially outwardly by impeller  11  in a direction towards the rear of the fan and into duct adaptor  7 . In use duct adaptor  7  will extend through a window or wall to the exterior of the building or may itself be fitted to a further conduit which extends to the exterior of the building. It may also be fitted in a duct in, for instance, a roof, ceiling or floor cavity. Appropriate circuitry and electronic components necessary to work the motor of the electric fan are provided on a circuit board that is located within a cavity (not shown) that is provided in the lower section of the rear of collector  19 .  
         [0047]     The internal housing of the above described electric fan collects the air discharging from impeller  11  and, in so doing, causes the air to expand thereby converting part of the kinetic pressure head to a static head. The extent to which such a conversion occurs depends on the system to which the blower is subjected, the system being the arrangement located either before the inlet to the device, or after its outlet or a combination of both. The level and efficiency of this conversion directly contributes to the capacity and overall efficiency of the fan as a whole.  
         [0048]     Essentially the above described fan receives air travelling in the direction of the main axis of the device and, through the rotating part of the device, causes it to leave in a radial direction. The air leaves via a collecting chamber which modifies the static and dynamic components of pressure and provides a discrete ducted direction to the air. The provision of multiple collecting chambers to receive air from a single rotating impeller, as provided by the above described fan, allows significant reductions in space for a given performance and without reduction in efficiency. In addition, with many smaller outlets from the multiple collecting chambers, changing the direction of the air to the axial directions is achieved much more efficiently.  
         [0049]     The location of the key moving and other parts of the above described fan around a single axis extending from the front to the rear of the device allows for the simple disassembly of at least some of these key components. This is particularly advantageous in that it allows the fan to be very simply maintained, in particular with regard to removing grease, cleaning generally, washing and disinfecting.  
         [0050]     Referring now to  FIG. 7  of the accompanying drawings, there is illustrated the central part of a fan similar to that described above. Items corresponding to those already mentioned in connection with the fan described above have been indicated with the same reference numerals. The airflow leading to discharge from the fan via duct adaptor  7  has been indicated by arrows  59 . Located on the outer surface of an internal partition  61  of collector  19  is a humidity sensor  58 . Provided adjacent and forward of humidity sensor  58  is a hole  63  in motor mount  15 . Opposite hole  63  and provided in the wall of collector  19 , adjacent and rearward of sensor  58 , is a further hole  65  which is aligned with hole  63 . Arrows  67  indicate the airflow through holes  65  and  63 , from the main airflow indicated by arrows  59 , and past and into contact with sensor  58 .