Abstract:
A drying apparatus includes an outer case, a portion of the outer case defining a cavity in which articles can be dried, an outlet disposed at the lower end of the cavity and a filter unit arranged downstream of the outlet, wherein the filter unit includes a particulate filter and a sterilising filter. By providing this filter unit including both a particulate filter and a sterilising filter, solid matter and bacteria can be removed from the waste liquid. This results in a hygienic and sanitary waste liquid output from the filter unit.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national stage application under 35 USC 371 of International Application No. PCT/GB06/004681, filed Dec. 14, 2006, which claims the priority of United Kingdom Application No. 0602075.4, filed Feb. 2, 2006, the contents of both of which prior applications are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to drying apparatus. Particularly, the invention relates to drying apparatus including a filter unit for removing particulates and bacteria from a waste liquid such as water. 
       BACKGROUND OF THE INVENTION 
       [0003]    Conventional arrangements for collecting and removing waste water from drying apparatus such as hand dryers are well known from, for example, U.S. Pat. No. 5,459,944. Waste water is collected via a duct or similar and transferred to a drip collector for subsequent manual removal. Such storage of waste water is unhygienic, may lead to the spread of bacteria and requires regular maintenance to empty the drip collector and maintain a sanitary environment. 
         [0004]    The addition of an antibacterial water absorption sheet with a large surface area to encourage evaporation is known from JP 11-18999 A. This counters some of the problems of bacterial infestation and results in less frequent emptying of a water collector. However, particulate matter will be deposited on the sheet, and this will affect the performance of the machine over time and require frequent cleaning. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to provide drying apparatus which is capable of filtering and sterilising liquid more efficiently and reliably than prior art apparatus. 
         [0006]    The invention provides drying apparatus comprising an outer case, a portion of the outer case defining a cavity in which articles can be dried, an outlet disposed at the lower end of the cavity and a filter unit arranged downstream of the outlet, wherein the filter unit comprises a particulate filter and a sterilising filter. By providing a filter unit comprising a particulate filter and a sterilising filter, solid matter and bacteria can be removed from the waste liquid. This results in a hygienic and sanitary waste liquid output from the filter unit. 
         [0007]    Preferably, the sterilising filter is located downstream of the particulate filter. By this arrangement, the particulate filter can remove some solid material and larger particulates from the waste liquid to prevent the sterilising filter from clogging. 
         [0008]    Preferably, the filter unit further comprises flow directing means for guiding liquid through the filter unit. By providing flow directing means, the liquid can be directed to flow through the sterilising filter. The flow directing means allow efficient use of the sterilising filter ensuring that the water leaving the filter unit has been sufficiently treated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    An embodiment of the invention will now be described with reference to the accompanying drawings, in which: 
           [0010]      FIG. 1   a  is a perspective view of a hand dryer according to the present invention; 
           [0011]      FIG. 1   b  is a side view of the hand dryer of  FIG. 1   a;    
           [0012]      FIG. 2  is a section through the hand dryer of  FIG. 1   a  showing a filter unit; 
           [0013]      FIG. 3  is an enlarged version of part of  FIG. 2  showing the internal workings of the hand dryer and the filter unit in greater detail; 
           [0014]      FIG. 4  is a perspective view of a liquid treatment module including the filter unit removed from the hand dryer of  FIG. 1   a;    
           [0015]      FIG. 5   a  is perspective view from above of the hand dryer of  FIG. 1   a  showing the liquid treatment module partially removed from the hand dryer; and 
           [0016]      FIG. 5   b  is a perspective view from below of the hand dryer of  FIG. 1   a  showing the liquid treatment module partially removed from the hand dryer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]      FIGS. 1   a  and  1   b  show a hand dryer  10  according to the present invention. The hand dryer  10  includes an outer case  12 , a front wall  14   a , a rear wall  14   b , two side walls  14   c ,  14   d  and a cavity  16 . The rear wall  14   b  may include elements suitable for attaching the hand dryer  10  to a wall surface or other suitable fixture. Elements for connecting the hand dryer  10  to a power source may also be included. 
         [0018]    The cavity  16  is defined by opposing arcuate front and rear walls  16   a ,  16   b . The cavity  16  is open at its upper end  18 , and the dimensions of the opening are sufficient to allow a user&#39;s hands (not shown) to be inserted easily into the cavity  16  for drying. A high-speed airflow is generated by a motor unit having a fan (not shown). The motor unit and fan are located inside the outer case  12 . The high-speed airflow is expelled through two slot-like openings  20  disposed at the upper end  18  of the cavity  16  to dry the user&#39;s hands. These features are not material to the present invention and will not be described any further here. The cavity  16  is open at the sides as can be seen in  FIGS. 1   a  and  1   b.    
         [0019]    As can be seen from  FIG. 2 , a drain channel  22  is located at the lower end  24  of the cavity  16 . The drain channel  22  is delimited by the lower edges of the front wall  16   a  and the rear wall  16   b  of the cavity  16  and slopes downwardly towards one side of the cavity  16 . An outlet  26  is located in the drain channel  22 . The outlet  26  can take any suitable form. In this embodiment, it comprises a circular aperture with a central plug  26   a . The outlet  26  and plug  26   a  delimit a narrow, annular opening. 
         [0020]    Referring to  FIGS. 2 and 3 , a chamber  40  is formed in a lower part of the outer case  12  below the cavity  16 . The chamber  40  is delimited by a plurality of chamber walls  40   a  and has an open lower end. A liquid treatment module  30  is located in the chamber  40  and is held in place by clips, quarter turn fastenings or other fastening means (not shown). 
         [0021]    Referring to  FIGS. 3 and 4 , the liquid treatment module  30  includes a filter unit  200 . The filter unit  200  is designed to filter particulates and impurities from the water, and to kill bacteria in the water. A filter inlet  202  is located at the upper end of the filter unit  200  and communicates with the outlet  26 . A sump  204  is located downstream of the filter inlet  202 . The sump  204  has a base  204   a . A wall  206  of the sump forms a weir  206   a . The height of the weir  206   a  determines the maximum level of liquid that can be contained within the sump  204 . A filter outlet  208  is delimited by the weir  206   a , the wall  206  of the sump  204  and the outer walls  210  of the filter unit  200 . The filter outlet  208  provides an outlet for water flowing over the weir  206   a.    
         [0022]    A partition  212  extends from the upper portion of the filter unit  200  adjacent the filter inlet  202  into the sump  204 . The partition  212  extends partially into the sump  204  such that the distal end  212   a  of the partition  212  is spaced from the base  204   a  of the sump  204 . The partition  212  is arranged such that the volume of a first region  204   b  of the sump  204  beneath the filter inlet  202  is greater than a second region  204   c  of the sump  204  adjacent the weir  206   a.    
         [0023]    A sterilising filter  214  is located at the base  204   a  of the sump  204 . The sterilising filter  214  consists of particles of an iodine-loaded resin. The resin is loaded at a concentration of 500 g/l. In this embodiment, the volume of the sterilising filter  214  is 50 ml. The iodine-loaded resin acts as a sterilising compound to kill any bacteria present in the water. The particles of the sterilising filter  214  are substantially spherical and have dimensions in the range of 0.1 to 2 mm (average particle size 0.8 mm). The sterilising filter  214  is dimensioned such that the distal end  212   a  of the partition  212  extends partially into the sterilising filter  214 . 
         [0024]    A particulate filter  216  is located above the sterilising filter  214  and comprises glass beads with diameters of 4 mm. The particulate filter  216  is located on top of the sterilising filter  214  in the first region  204   b  beneath the filter inlet  202  which is bounded by the partition  212  and the sump  204 . The particulate filter  216  has a volume of 10 ml. Further, the particulate filter  216  operates as a pre-filter, preventing larger particles of solid matter (in particular soap) from blocking the sterilising filter  214 . In order to improve performance, the area of the bed of the particulate filter  216  and sterilising filter  214  is maximised. A large bed area reduces the pressure drop across the filters and increases the resistance of the filters to fouling and becoming blocked. 
         [0025]    Both the sterilising filter  214  and the particulate filter  216  are located in the sump  204  below the maximum level of liquid that can be contained in the sump  204 . This means that, once the level of liquid in the sump  204  has reached the maximum, operational, level, the sterilising filter  214  and the particulate filter  216  are completely submerged in the water. This is beneficial because the sterilising filter  214  is prone to cracking and forming air pockets if it is permitted to dry out once it has become wetted. By keeping the sterilising filter  214  continuously wetted, this problem is avoided. In addition, this configuration ensures that the water flow is well distributed. Further, the maximum level of liquid should be far enough above particulate filter  216  to allow the head of water to apply pressure on the bed of the filters. 
         [0026]    The liquid treatment module  30  further includes a liquid dispersion unit  35  located below the filter unit  200 . The liquid dispersion unit  35  is arranged to receive water from the filter outlet  208 . An exhaust conduit  37  located within the liquid dispersion unit  35  provides a communication path from the liquid dispersion unit  35  to the outside of the outer case  12  of the hand dryer  10 . The liquid dispersion unit  35  further includes a collector  100  for collecting water from the filter outlet  208 . The collector  100  has a base  100   a . A high frequency agitator in the form of a piezo-electric device  102  is located at the base  100   a . A fan  104  is supported on one of the chamber walls  40   a . The fan  104  is located outside the chamber  40  separate from the liquid treatment module  30 . The fan  104  is configured to direct an airflow into the collector  100  through an aperture  38  provided in the liquid treatment module  30 . 
         [0027]    In use, the water removed from a user&#39;s hands during the drying process flows down the front wall  16   a  and the rear wall  16   b  of the cavity  16  and into the drain channel  22  disposed at the lower end  24  of the cavity  16 . The drain channel  22  collects and guides the water towards the outlet  26 . 
         [0028]    Upon entering the outlet  26 , the water passes into the filter unit  200  through the filter inlet  202  (see arrow A). The water falls onto the particulate filter  216  (arrow B) and spreads evenly across the surface of the particulate filter  216 . As the water moves down through the beads of the particulate filter  216  under the influence of gravity, larger particles of dirt and debris will be left behind in the particulate filter  216 . When the water reaches the sterilising filter  214  (arrow C), the majority of the solid particulates in the water will have been removed by the particulate filter  216 . 
         [0029]    The sterilising filter  214  sterilises the water by deactivating bacteria in the water. The iodine-loaded resin releases iodine into the water at a rate of 1 to 5 parts per million (ppm). Iodine is a strong oxidant and hence acts as broad spectrum antimicrobial. The water flows down through the sterilising filter  214 , is sterilised and is then deposited in the bottom of the sump  204 . This process continues and the volume of water collected in the sump  204  increases until it reaches the maximum level permitted by the weir  206   a . Up until this point, the water levels either side of the partition  212  experience an equal force due to atmospheric pressure. However, if more water is introduced through the filter inlet  202 , the increased head of water in the first region  204   b  will cause an imbalance in the forces acting on the water levels either side of the partition  212 . The effect of this is for the mass of the added water to apply a force downwardly on the water in the sump  204 . This causes a net movement of water in the direction shown by the arrow D. The partition  212  directs the flow of water down towards the base  204   a  of the sump  204 , down through a part of the sterilising filter  214  located in the first region  204   b  of the sump  204 , and back up through another part of the sterilising filter  214  located in the second region  204   c  of the sump  204  to the weir  206   a . Therefore, the partition  212  forces the water to follow a convoluted path from the filter inlet  202  to the weir  206   a . In this embodiment, the convoluted path is in the form of a U-shaped path. If the partition  212  were not present, then water entering the sump  204  would tend to flow over the weir  206   a  without passing through the sterilising filter  214 , and sterilisation would not take place. 
         [0030]    The excess water, now sterilised, spills over the weir  206   a  (arrow E) and flows down the filter outlet  208 . The water collects at the base  100   a  of the collector  100  which is in communication with the piezo-electric device  102 . The piezo-electric device  102  is set to oscillate at a pre-determined frequency and magnitude such that sufficient vibrational energy is imparted to water molecules on the surface of the water in the collector  100  to overcome surface tension effects. Therefore, the water is turned into a fine mist in the interior space of the collector  100 . 
         [0031]    The fan  104  directs an airflow downwardly into the collector  100 . This directs the fine mist towards, and down, the exhaust conduit  37  which leads to the outside of the outer case  12 . This process continues until all the water contained within the collector  100  is efficiently and hygienically removed from the collector  100 . 
         [0032]      FIGS. 5   a  and  5   b  illustrate the removal of the liquid treatment module  30  from the outer case  12  for maintenance or replacement. The liquid treatment module  30  is removed downwardly from the hand dryer  10 . In this embodiment, the filter  200  forms part of the liquid treatment module  30  and is removable from the outer case  12  with the liquid treatment module  30 . 
         [0033]    It will be understood that the invention is not to be limited to the precise details described above. Other variations and modifications will be apparent to the skilled reader. 
         [0034]    For example, the drying apparatus need not take the form of a hand dryer. The drying apparatus could be a condenser-type laundry dryer. In such a laundry dryer, water evaporated from wet textiles in the drum (cavity) of the laundry dryer can be condensed, filtered by a filtration unit and then removed by agitation or evaporation. 
         [0035]    Further, the invention could be utilized in other forms of drying apparatus; for example, other forms of domestic or commercial drying apparatus such as washer-dryers, ventilation-type laundry dryers or full-length body dryers. 
         [0036]    Additionally, other forms of liquid dispersion unit can be used to disperse the collected liquid; for example, an ultrasonic generator, a fan, a heating element or electrolysing apparatus. Any of these devices could be used in place of a piezo-electric device to agitate, evaporate or electrolyse the water (or other liquid) as required. 
         [0037]    The liquid treatment module need not be located inside a chamber present in the drying apparatus. Other arrangements are possible; for example, the module could form a part of the outer case, or could be mounted on or outside the outer case of the drying apparatus. 
         [0038]    Further, the liquid treatment module need not be removed from the lower part of the drying apparatus. The liquid treatment module may form part of the upper side or top of the drying apparatus, and be removed sideways or upwardly depending upon the requirements of the drying apparatus. Additionally, it need not be removable and could remain fixed inside the drying apparatus. 
         [0039]    As a further variation, other forms of airflow generator are possible. For example, an air bleed or exhaust airflow could be taken from a motor unit. For example, the motor unit for driving the drying process of the hand dryer has a fan. This fan could be used to generate an airflow to vent the evaporated water to the outside of the drying apparatus rather than using an additional fan. 
         [0040]    Additionally, the dimensions of the glass beads need not be 4 mm. They may be varied in size from 1 mm to 6 mm. Additionally, other types of particulate filter media could be used; for example, glass-fibre brushes, plastic brushes, porous ceramics, plastic beads or small stones. What is important is that the particulate filter is formed from an inert material with a density greater than 1 g/l. The size of the particulate filter may be varied and may be any size suitable to ensure that the majority of the particulates are filtered and removed from the water to prevent the sterilising filter from clogging and becoming blocked. 
         [0041]    As an additional variation, a number of particulate filters may be provided. They may be located outside of the sump, for example in the filter inlet to pre-filter water before it reaches the sump. 
         [0042]    The sterilising filter need not be formed of a resin with substantially spherical particles with dimensions in the range of 0.1 to 2 mm. Other particle shapes or sizes could be used, for example by grinding. Alternatively, a single, porous block of resin could be used. Further, the sterilising filter need not be formed from a resin. Other inorganic host media could be used; for example, inorganic polymers, metal chelates, metal complexes or crystal structures. 
         [0043]    The loading of iodine need not be 500 g/l and may be within a preferred range of 300 g/l to 600 g/l. Further, the concentration of iodine released into the water may also be outside the range of 1 to 5 ppm. What is important is that the concentration is high enough to kill the bacteria in the water whilst low enough to avoid discolouring the water. Further, the volume of the sterilising filter can be varied, provided it is sufficient to sterilise the water. 
         [0044]    Additionally, the anti-bacterial agent in the sterilising filter need not be iodine and could include alternative bacteria-killing media; for example, a halogen-containing material or a precursor to a halogen-containing material. Typical, non-exhaustive, examples of these are materials including: Chlorine, Bromine, Iodine, Hypochlorite or Hypobromide. Alternatively, other methods of sterilising bacteria may be implemented; for example, Titanium dioxide or UV-radiation activated silver nanoparticles. 
         [0045]    Further, the particulate filter and sterilising filter need not be located wholly in the sump. They could be located above the sump, out of the water in the sump, or partially submerged in the water in the sump. 
         [0046]    As a further variation, the particulate-filtering media and the bacteria-killing media need not form separate stages in the filter and may be combined to form a single unit. 
         [0047]    As a further variation, the filter need not be removable from the drying apparatus. The filter could remain inside the casing of the drying apparatus when the liquid treatment module is removed. The filter could either be removable separately from the liquid treatment module or be fixed permanently inside the casing of the drying apparatus.