Abstract:
Drying apparatus includes a housing defining an air inlet and a tortuous airflow passage leading to at least one air outlet. The outlet comprises two upright sets of louvres. An impeller is arranged to draw air into the inlet, through the airflow passage and to expel it via the outlet. A set of infrared emitting heating elements is located in the airflow passage behind a screen or glass panel and arranged both to radiate heat directly outwardly from the housing and to heat air in the airflow passage. Additional resistance heating elements are located in the airflow passage. The apparatus has a control system including a user interface, and is arranged to control the operation of the impeller and the two different kinds of heating elements in response to user input. The apparatus includes a heatsink associated with the infrared heating elements, which is located so that air passing through the airflow passage contacts the heatsink. The control system is arranged, in at least one mode of operation, to pre-heat the heatsink by operating the infrared heating elements prior to operating the impeller.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    THIS invention relates to a drying device or apparatus which can be used for drying a person&#39;s body after bathing or showering, for example. 
       SUMMARY OF THE INVENTION 
       [0002]    According to the invention there is provided drying apparatus including a housing, the housing defining an air inlet, at least one airflow passage, and at least one air outlet; an impeller arranged to draw air into the inlet, through the airflow passage and to expel it via the outlet; at least one first heating element located in or adjacent to the airflow passage and arranged both to radiate heat directly outwardly from the housing and to heat air in the airflow passage; and a control system including a user interface and arranged to control the operation of the impeller and said at least one first heating element in response to a user input. 
         [0003]    The drying apparatus may include a heatsink associated with said at least one first heating element and located so that air passing through the airflow passage contacts the heatsink, the control system being arranged, in at least one mode of operation, to pre-heat the heatsink by operating said at least one first heating element prior to operating the impeller. 
         [0004]    Preferably, the first heating element comprises an infrared emitting element operable to generate an infrared output with a wavelength in a predetermined range, typically 7 to 14 microns. 
         [0005]    The apparatus may include a plurality of infrared emitting elements located one above the other and arranged to emit infrared radiation towards a user of the apparatus. 
         [0006]    The plurality of infrared emitting elements may be located behind a cover defining a part of the airflow passage, the cover being substantially transparent to infrared radiation. 
         [0007]    The apparatus may include at least one second heating element located in or adjacent to the airflow passage and arranged to be operated selectively to heat air in the airflow passage. 
         [0008]    Said at least one second heating element may comprise a resistance heating element, for example. 
         [0009]    The control system is preferably arranged to operate said at least one first heating element, said at least one second heating element and said impeller selectively so as to limit the maximum power consumption of the drying apparatus to below a predetermined value. 
         [0010]    In an embodiment of the apparatus, the control system is arranged to receive a user input selecting one of a plurality of pre-programmed operating modes, each operating mode being defined by a different combination of operating conditions for the first and second heating elements and the impeller. 
         [0011]    The apparatus may include an ultraviolet light source in or adjacent to the airflow passage and arranged to sterilize air passing through the airflow passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a pictorial view of a drying device according to the invention; 
           [0013]      FIG. 2  is a sectional side view on the line  2 - 2  in  FIG. 1 ; 
           [0014]      FIG. 3  is a section on the line  3 - 3  in  FIG. 1 ; 
           [0015]      FIG. 4  is a section on the line  4 - 4  in  FIG. 1 ; 
           [0016]      FIG. 5  is a simplified schematic block diagram of a control system of the drying device; 
           [0017]      FIGS. 6 to 9  are flow diagrams illustrating the functioning of the apparatus in use; and 
           [0018]      FIGS. 10(   a ) To  10 ( c ) are waveform diagrams illustrating a power control scheme utilised by the control system of the device. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0019]    The drying device illustrated in  FIGS. 1 to 4  comprises a housing or cabinet  10  which is generally rectangular in front elevation and which is of the same general height as a human, typically in the range of 1.5 to 2 meters tall. The housing is designed to be as shallow as possible and has a typical front to back depth of approximately 20 cm. 
         [0020]    On its front surface  12 , the drying device has a central, upright cover panel  14  which covers a plurality of infrared emitters (see below) and which is transparent to infrared radiation. The panel  14  can comprise, for example, suitable glass or a metal mesh. 
         [0021]    On either side of the panel  14  are sets of adjustable louvres  16  and  18  which are normally closed, as illustrated, but which are opened in use to emit a flow of heated air towards a user of the device. 
         [0022]    At the upper end of the housing  10  is a large display panel  20  with loud speakers  22  and  24  on either side of it. The loudspeakers form part of an optional audio and/or video system that can be included in the device. For example, the system can include a radio or TV tuner, a docking station for an iPod™ or other portable music player, or other conventional audio visual technology. The display panel  20  displays the status of the drying device and serves as part of a user interface in conjunction with a remote control unit  26 . The display panel can comprise a liquid crystal display (LCD) or any other suitable type of display. Low voltage display technologies are preferred due to the fact that the device is likely to be used in a humid environment. 
         [0023]    As can be seen from  FIG. 1 , the drying device has a neat and sleek appearance and is designed to be as unobtrusive as possible when installed in a bathroom or another desired location, typically against a wall. 
         [0024]    The housing  10  may be fixed to a wall or other support, or can be provided with wheels or rollers to permit it to be moved about as required. 
         [0025]    As best shown in  FIGS. 2 and 3 , the housing defines an inlet  28  for air at the lower end of its front surface  12 . From the inlet, a tortuous airflow passage is defined within the interior of the housing. Air entering the inlet  28  is first drawn up a central inlet passage  30  which is defined between the panel  14  and an upright heatsink structure  32  located within the housing. Mounted on the heatsink structure are four infrared emitting panels  34 , one above the other. Air reaching the top of the inlet passage  30  then flows down a further passage  36  defined between a finned rear surface of the heatsink structure and the rear surface  38  of the housing. Vertical fins  40  formed on the rear of the heatsink structure, which is typically an aluminum extrusion, extend into the passage  36  so that air passing downwardly through the passage  36  contacts the fins. 
         [0026]    An ultraviolet emitting fluorescent tube  42  is mounted vertically in the passage  36  so that air passing through the passage  36  is subjected to UV light. The purpose of the UV lamp is to sterilize air passing through the device, and also to sterilize the interior of the housing  10 . 
         [0027]    At the lower end of the passage  36 , near the base  44  of the housing  10 , is a centrally located centrifugal fan  46  which has a forward facing inlet  48 . Other types of fan could be used instead. The lower end of the airflow passage  36  opens into a chamber or plenum  50  below the heatsink structure  32 , directing air to the inlet  48  of the fan  46 . 
         [0028]    The fan  46  has a pair of opposed outlets  52 . 1  and  52 . 2  which direct air into respective passages  54  and  56  in the base of the device. The passages  54  and  56  have short horizontal portions which turn through 90 degrees to define vertical, tubular air distribution conduits  58  and  60  which distribute air upwardly in the housing adjacent to the respective sets of louvres  16  and  18 . In each of the conduits  58  and  60 , a respective vertically extending slot  62  and  64  releases air from the conduit outwardly in the direction of the arrows in  FIG. 3  when the louvres are opened. 
         [0029]    To sum up airflow in the device, therefore, ambient air enters the device via the inlet  28  at the front of the housing, travels upwardly through the inlet airflow passage  30  past the infrared emitters  34  and the forward facing surface of the heatsink structure  32 , down the airflow passage  36 , past the finned rearward facing surface of the heating structure  32  and the ultraviolet lamp  42 , to the chamber  50  adjacent the inlet of the centrifugal fan  46 . From the fan  46 , air is expelled into the respective passages  54  and  56 , and up the vertical conduits  58  and  60 , from which it is released by the respective slots  62  and  64  and the sets of louvres  16  and  18  from the front of the housing. 
         [0030]    Within the conduits  58  and  60  are located resistance heating coils  66  and  68  which can be operated to increase the temperature of air passing through the conduits in use. 
         [0031]    The conduits  58  and  60  are rotatable about their long axes, through about 90 degrees, so that the direction of the airstreams emitted via the sets of louvres  16  and  18  can be continuously swung back and forth from left to right in use, in opposite directions, or adjusted to a preferred static direction. The sets of louvres themselves are also adjustable to allow the device to cater for users of different height, for example. Both the conduits and the louvres are moved by drive mechanisms comprising small electric motors and suitable gearing or drive linkages. When the device is not in use, the louvres are closed, preventing excess dust and moisture from entering the device and presenting a neat appearance. 
         [0032]    The operation of the device and its control system will now be described in greater detail. 
         [0033]    Conventional drying devices using a flow of heated air, such as hand dryers used in public toilets, for example, typically comprise a fan and one or more heating coils. When the device is actuated, whether by a switch mounted on the housing of the device or by a sensor detecting the presence of a users&#39; hands, for example, the fan is operated and the heating coils are connected to the AC mains electrical supply, generating the required stream of hot air. 
         [0034]    Conventional hand drying devices of this kind typically have a power consumption in the range of 1.6 to 3 kW. If a device of this general kind is scaled up sufficiently to be able to provide a strong flow of sufficiently warm air to dry a users&#39; entire body effectively, its power consumption will be substantially greater and could approach or exceed 10 kW. Although this can, in principle, be done, installation of such a device will then require a dedicated electrical feed (and possibly a three-phase supply). If it is desired to make the device usable in existing premises, it is necessary to limit the peak power consumption of the unit to a level that can safely be supplied by a single conventional wall outlet. For example, in South Africa, where the nominal AC mains voltage is 220V and conventional wall outlets are rated at 15 A, the maximum power consumption of the device must be limited to 3.3 kW. 
         [0035]    The total power consumption of the infrared panels  34 , the heating coils  66  and  68 , the fan  46 , the UV light  42  and the other electrical and electronic components of the prototype drying device of the invention was in the region of 5 kW. It therefore becomes necessary to manage the power consumption of the various components of the device to ensure that a safe maximum predetermined power consumption value of approximately 3 kW is not exceeded at any time. 
         [0036]    In addition, in order to control the wavelength of infrared radiation emitted by the infrared emitting panels  34 , it is necessary to control their temperature and thus the power dissipated in these panels. 
         [0037]    Referring now to  FIG. 5 , which is an overall schematic block diagram of the control system of the drying device, the control system is seen to comprise a main control module  70  and a user interface  72 . The user interface comprises the remote control unit  26  and the display  20 , as well as a sensor (not shown) responsible to the remote control. The control module  70  is microprocessor-based and will typically comprise a suitable microprocessor with associated read only memory (ROM) in which software controlling the operation of the device is stored, and random access memory (RAM) for storing user preferences and settings, and other temporary data. 
         [0038]    As indicated in  FIG. 5 , the control module receives three user selected inputs as well as a number of feedback signals from sensors in the device. 
       The Inputs to the Control Module are: 
       [0000]    
       
         
           
             1. User selection: Temperature 
             2. User selection: Mode 
             3. User selection: Outlet air speed 
             4. Feedback: Fan speed 
             5. Feedback: Inlet air temperature 
             6. Feedback: Outlet air temperature 
             7. Feedback: Internal casing temperature 
             8. Feedback: Fault conditions in Air heater coil, IR panel, or UV power modules 
           
         
       
     
         [0047]    The control module also generates several outputs, both to the user interface  72  and to various circuits and control modules of the device. 
         [0000]    Outputs from the Control Module are:
       1. Control: IR panel power   2 Control: Air coil power   3. Control: Fan speed   4. Control: UV control   5. User interface: fault   6. User interface: outlet air temperature   7. User interface: IR wavelength parameter       
 
         [0055]    Apart from the above mentioned microprocessor based control module, the control system of the drying device includes a number of sensor units and a number of power modules for controlling the operation of the various electrically powered components of the device. Thus, an infrared (IR) power module  74  is provided to control the power supplied to the infrared emitting panels  34 , a heating coil power module  76  is provided to control the electrical supply to the heating coils  66  and  68 , a fan power module  78  is provided to control the operation of the centrifugal fan  46  and a UV power module  80  is provided to control the operation of the UV lamp  42 . 
         [0056]    In addition, the control module receives a number of input and/or feedback signals, including signals from a number of temperature sensors. An outlet air temperature sensor  82  provides an outlet air temperature signal via a measurement circuit  34 , and similar temperature sensors  86  and  88  which measure the temperature of the inlet airstream and the internal temperature within the housing of the device provide respective signals to the control module via measurement circuits  90  and  92 . 
         [0057]    The entire control system is powered by a mains-derived power supply of a conventonal nature (not shown). 
         [0058]    The drying device has a number of operating modes which can be selected by a user via the user interface  72 . The following predetermined modes were programmed into the prototype unit:
       Immediate air heat: Air heater coils on maximum power, blower fan on to create design air flow rate, power to IR panels modulated.   Immediate IR heat: IR panels on maximum power, power to air heater coils modulated, blower fan on low.   Auto heat (uses preheat): blower fan will start when sufficient preheat time has elapsed to ensure that outlet air will be at user defined temperature with blower fan operating at user defined speed. Power to air heater coils and IR panels modulated according to user temperature selection.   Sauna: Fan speed zero, air coils zero, panels operated at 175 W per panel.   Timed: combines fan speed, air heating coils power, and IR panel power in a predetermined profile.       
 
         [0064]    It can be seen that the various modes or profiles are determined by different combinations of operating conditions for the infrared emitting panels, the heating coils and the fan. It will be appreciated by those skilled in the art that other predetermined operating modes can be devised and that the described modes are purely exemplary. 
         [0065]    In each mode, the control module monitors the various inputs, including user settings, and controls the operation of the relevant components of the device via the respective power modules in accordance with an overall controlling algorithm. The overall algorithm includes total power output limiting, infrared wavelength control of the IR panels, correlation of temperature mappings to detect possible dangerous operating regions, failure monitoring (for example, fan speed not following fan speed control signal), determination of infrared panel temperature from timing and power supply data, and profiling of other parameters such as fan speed rate of change of switch-on to avoid uncomfortably high outlet air temperatures. 
         [0066]    In the prototype device, it is a feature of the control method that no temperature feedback is required from the infrared panels. Instead, the control module contains detailed mappings of the infrared panel warm-up and operating temperatures in terms of time and input power, which are used to determine panel temperature. 
         [0067]    From this information, it is possible to determine (using data supplied by the infrared panel manufacturers) the wavelength of infrared light emitted by the panels  34  in the different operating modes. Thus, in the “sauna” mode, the infrared panels are operated so as to emit infrared radiation in a preferred spectrum, typically in the range of 7 to 14 microns. 
         [0068]    In the prototype unit, Ceramicx FTE 500 infrared emitters were used, which are rated for operation at 500 W. A graph published by the manufacturer, showing the output spectral power density against wavelength of the unit, indicates a peak in the region of 6 microns when operating at its rated power. However, by modulating the power fed to the unit, and running it at a power in the range of 175 to 250 W, an infrared output in the desired wavelength range is obtained. 
         [0069]    Apart from the abovementioned control signals, the power modules  74 ,  76 ,  78  and  80  are arranged to provide feedback signals to the control modules  70  indicative of fault conditions that may arise. Such fault conditions include zero current draw by the relevant component, over-temperature of the respective power module or excessive current draw by the component in question. In the case of the infrared power module  74 , the power module detects zero current draw or excessive current draw by any of the panels, thus enabling failure of one of the four panels to be detected. 
         [0070]    The power modules control the power to the respective components in response to control signals from the control module. Modulation of the power supplied to the components is achieved by controlling the shape of the AC waveform supplied to the applicable component. The power modules comprise triacs or dual silicon controlled rectifiers (SCRs) and associated circuitry such as snubbers. Where the component is to be operated at full power, the full AC waveform is applied. To reduce the power output of the component, the AC waveform is progressively truncated. In this way, the control module is able to supply accurately the required power to the relevant component.  FIGS. 10(   a ) and ( b ) show truncated AC waveforms corresponding to 25% and 50% power, whereas  FIG. 10(   c ) shows a full AC waveform corresponding to 100% power. 
         [0071]    The operating modes and sequences of the described device are set out diagrammatically in the flowcharts of  FIGS. 6 to 9 . 
         [0072]    A significant feature of the device is a preheating function which operates the infrared emitters  34 , causing them to heat the heatsink structure  32 . Being a substantial aluminum extrusion, the heatsink structure can store a significant amount of heat. This allows the temperature of the output airflow to be increased, for a given airflow rate, or alternatively allows the airflow rate to be increased for a given output air temperature. The “autoheat” operating mode makes use of this feature, first operating the infrared units  34  to raise the temperature of the heatsink (taking into account a user selected outlet air temperature) and then starting the fan  46  once sufficient preheating has taken place. The heating elements  66  and  68  are then operated to further heat the preheated air, with the power to the infrared panels and the heating coils being modulated to maintain overall power consumption below the predetermined maximum level. 
         [0073]    The heating device can also be operated in a “sauna” mode in which it relies entirely on the infrared output of the IR emitters  34 , or the other modes referred to above, so that a user can select a preferred mode according to circumstances. 
         [0074]    It will be appreciated that the above described drying device is versatile and efficient, and enables effective drying to be achieved notwithstanding a limited maximum input power consumption.