Abstract:
A drying apparatus has a casing, a cavity formed in the casing for receiving an object, and a fan located in the casing and creating an airflow. At least one slot-like opening communicates with the fan and is arranged in the casing so as to direct an airflow transversely across the cavity. The slot-like opening is formed between opposing walls which are manufactured from a thermosetting plastics material. By manufacturing the walls of the slot-like opening from a thermosetting plastic material such as melamine, the walls of the slot-like opening can be molded economically instead of machined from metal. The thermosetting plastic material is dimensionally stable when moulded, thermally resistant and impact resistant.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application under 35 USC 371 of International Application No. PCT/GB2006/002138, filed Jun. 12, 2006, which claims the priority of United Kingdom Application Nos. 0515744.1, filed Jul. 30, 2005, and 0600881.7, filed Jan. 17, 2006, the contents of which prior applications are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a dryer which makes use of narrow streams of high velocity, high pressure air to dry a user&#39;s hands. 
     BACKGROUND OF THE INVENTION 
     The use of air jets to dry hands is well known. Examples of hand dryers which have at least one slot-like opening emitting at least one air jet for the purposes of drying hands are shown in GB 2249026A, JP 2002 034835A and JP 2002306370A. However, the efficient operation of such drying apparatus depends of the provision of slot-like openings which have a constant width along the length of the opening. The cost-effective manufacture of such openings presents certain difficulties, particularly when the airflow emitted through the openings is at a relatively high temperature. Commonly, the slot-like openings of the prior art apparatus have been manufactured from metal (such as stainless steel or aluminium) which increases the weight cost of the product. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide drying apparatus which, in use, dries an object efficiently and is more economical to manufacture than the prior art devices. It is another object to provide an improved hand dryer in which the manufacturing costs are reduced in comparison to the prior art. 
     The invention provides drying apparatus having a casing, a cavity formed in the casing for receiving an object, a fan located in the casing and capable of creating an airflow, and at least one slot-like opening communicating with the fan and arranged in the casing so as to direct an airflow transversely across the cavity, wherein the slot-like opening is formed between walls which are manufactured from a thermosetting plastics material. 
     By manufacturing the walls of the slot-like opening from a thermosetting plastics material such as melamine, the walls of the slot-like opening can be moulded economically instead of machined from metal. The thermosetting plastics material is dimensionally stable when moulded, thermally resistant and impact resistant. 
     Preferably, the maximum width of the slot is no more than 0.5 mm, more preferably between 0.3 mm and 0.4 mm. In a preferred embodiment, the slot-like opening has a constant width along its length. 
     It is preferred that at least one upstanding member is provided between the opposing walls of the slot-like opening. The or each upstanding member is preferably shaped so as to minimise the introduction of turbulence to an airstream emitted through the slot-like opening when the drying apparatus is in use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the invention will now be described with reference to the accompanying drawings, in which: 
         FIG. 1  is a side view of drying apparatus according to the invention in the form of a hand dryer; 
         FIG. 2  is a perspective view of the hand dryer of  FIG. 1 ; 
         FIG. 3  is a side sectional view of the hand dryer of  FIG. 1 ; 
         FIG. 4  is a side sectional view, shown on an enlarged scale, of the upper ends of the air ducts forming part of the hand dryer of  FIG. 1 ; 
         FIG. 5  is a schematic sectional side view, shown on a further enlarged scale, of the slot-like opening located in the front wall of the cavity of the hand dryer of  FIG. 1 ; 
         FIG. 6  is a schematic sectional side view, shown on the same further enlarged scale, of the slot-like opening located in the rear wall of the cavity of the hand dryer of  FIG. 1 ; 
         FIG. 7   a  is a schematic sectional side view of an alternative arrangement of a slot-like opening located in the cavity of the hand dryer of  FIG. 1 ; 
         FIGS. 7   b  and  7   c  are plan views of two alternative designs of an upstanding member located in the slot-like opening of  FIG. 7   a;    
         FIG. 8   a  is a plan view of the cavity entrance of a hand dryer according to a second embodiment of the invention; and 
         FIG. 8   b  is a front view of the slot-like opening located in the rear wall of the cavity of the hand dryer of  FIG. 8   a.    
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring firstly to  FIGS. 1 and 2 , the hand dryer  10  shown in the drawings comprises an outer casing  12  having a front wall  14 , a rear wall  16 , an upper face  18  and side walls  20 ,  22 . The rear wall  16  can incorporate fixing devices (not shown) for securing the hand dryer  10  to a wall or other structure prior to use. An electrical connection (not shown) is also provided on the rear wall or elsewhere on the casing  12 . A cavity  30  is formed in the upper part of the casing  12  as can be seen from  FIGS. 1 and 2 . The cavity  30  is open at its upper end and delimited thereat by the top of the front wall  14  and the front of the upper face  18 . The space between the top of the front wall  14  and the front of the upper face  18  forms a cavity entrance  32  which is sufficiently wide to allow a user&#39;s hands to be introduced to the cavity  30  through the cavity entrance  32 . The cavity  30  is also open to the sides of the hand dryer  10  by appropriate shaping of the side walls  20 ,  22 . 
     The cavity  30  has a front wall  34  and a rear wall  36  which delimit the cavity  30  to the front and rear respectively. Located in the lowermost end of the cavity  30  is a drain  38  which communicates with a reservoir (not shown) located in the lower part of the casing  12 . The purpose of the drain and reservoir will be described below. 
     As shown in  FIG. 3 , a motor (not shown) is located inside the casing  12  and a fan  40 , which is driven by the motor, is also located inside the casing  12 . The motor is connected to the electrical connection and is controlled by a controller  41 . The inlet  42  of the fan  40  communicates with an air inlet  44  formed in the casing  12 . A filter  46  is located in the air passageway connecting the air inlet  44  to the fan inlet  42  so as to prevent the ingress of any debris which might cause damage to the motor or the fan  40 . The outlet of the fan  40  communicates with a pair of air ducts  50 ,  52  which are located inside the casing  12 . The front air duct  50  is located primarily between the front wall  14  of the casing  12  and the front wall  34  of the cavity  30 , and the rear air duct  52  is located primarily between the rear wall  16  of the casing  12  and the rear wall  36  of the cavity  30 . 
     The air ducts  50 ,  52  are arranged to conduct air from the fan  40  to a pair of opposed slot-like openings  60 ,  62  which are located in the front and rear walls  34 ,  36  respectively of the cavity  30 . The slot-like openings  60 ,  62  are arranged at the upper end of the cavity  30  in the vicinity of the cavity entrance  32 . The slot-like openings  60 ,  62  are each configured so as to direct an airflow generally across the cavity entrance  32  towards the opposite wall of the cavity  30 . The slot-like openings  60 ,  62  are offset in the vertical direction and angled towards the base of the cavity  30 . 
       FIG. 4  shows the upper ends of the air ducts  50 ,  52  and the slot-like openings  60 ,  62  in greater detail. As can be seen, the walls  54   a ,  54   b  of the air duct  50  converge to form the slot-like opening  60  and the walls  56   a ,  56   b  of the air duct  52  converge to form the slot-like opening  62 . Even greater detail can be seen in  FIGS. 5 and 6 .  FIG. 5  shows that the slot-like opening  60  has a width of W 1  and  FIG. 6  shows that the slot-like opening  62  has a width of W 2 . The width W 1  of the slot-like opening  60  is smaller than the width W 2  of the slot-like opening  62 . The width W 1  is 0.3 mm and the width W 2  is 0.4 mm. 
     The walls  54   a ,  54   b ,  56   a ,  56   b  of the slot-like openings  60 ,  62  are moulded from a thermosetting plastics material, or thermosetting resin. These materials are dimensionally stable when subjected to the moulding process and are also thermally resistant at the required temperatures. The fact that the airflow exiting from the slot-like openings  60 ,  62  is only warmed by its passage past the motor means that the walls  54   a ,  54   b ,  56   a ,  56   b  are unlikely to be affected by the temperature of the airflow during normal use of the hand dryer. The thermosetting plastics materials are also impact resistant, which means that the walls  54   a ,  54   b ,  56   a ,  56   b  are able to withstand any impacts resulting from normal use of the hand dryer. 
     The walls  54   a ,  54   b ,  56   a ,  56   b  are formed by compression moulding. In the embodiment shown, the material used to form the walls  54   a ,  54   b ,  56   a ,  56   b  is melamine, although other materials such as urea-formaldehyde and phenolic resin could also be used. The material of the walls  54   a ,  54   b ,  56   a ,  56   b  also has antibacterial properties, in the form of either an antibacterial ingredient or a coating of an antibacterial substance. 
     Sensors  64  are positioned in the front and rear walls  34 ,  36  of the cavity  30  immediately below the slot-like openings  60 ,  62 . These sensors  64  detect the presence of a user&#39;s hands which are inserted into the cavity  30  via the cavity entrance  32  and are arranged to send a signal to the motor when a user&#39;s hands are introduced to the cavity  30 . As can be seen from  FIGS. 1 and 3 , the walls  54   a ,  54   b ,  56   a ,  56   b  of the ducts  50 ,  52  project slightly beyond the surface of the front and rear walls  34 ,  36  of the cavity  30 . The inward projection of the walls  54   a ,  54   b ,  56   a ,  56   b  of the ducts  50 ,  52  reduces the tendency of the user&#39;s hands to be sucked towards one or other of the walls  34 ,  36  of the cavity, which enhances the ease with which the hand dryer  10  can be used. The positioning of the sensors  64  immediately below the inwardly projecting walls  54   a ,  54   b ,  56   a ,  56   b  of the ducts  50 ,  52  also reduces the risk of the sensors  64  becoming dirty and inoperative. 
     As can be seen from  FIG. 2 , the shape of the cavity entrance  32  is such that the front edge  32   a  is generally straight and extends laterally across the width of the hand dryer  10 . However, the rear edge  32   b  has a shape which consists of two curved portions  33  which generally follow the shape of the backs of a pair of human hands as they are inserted downwardly into the cavity  30  through the cavity entrance  32 . The rear edge  32   b  of the cavity entrance  32  is substantially symmetrical about the centre line of the hand dryer  10 . The intention of the shaping and dimensioning of the front and rear edges  32   a ,  32   b  of the cavity entrance  32  is that, when a user&#39;s hands are inserted into the cavity  30  through the cavity entrance  32 , the distance from any point on the user&#39;s hands to the nearest slot-like opening is substantially uniform. 
       FIG. 7   a  shows an alternative configuration of one of the slot-like openings illustrated in  FIGS. 5 and 6 . In this alternative configuration, the slot-like opening  160  is formed between two walls  154   a ,  154   b  which approach one another along an axis  180 . The downstream end of each wall  154   a ,  154   b  is shaped so that a sharp corner is formed at the edge which is closest to the slot-like opening  160  but a smoothly curved edge is formed at the edge remote from the slot-like opening  160 . The sharp edge reduces turbulence and helps to maintain the velocity of the airflow as it leaves the slot-like opening whilst the curved edge reduces the risk of objects becoming caught on the protruding walls  154   a ,  154   b.    
     The walls  154   a ,  154   b  are each inclined to the axis  80  at an angle of 7°, giving an angle between the walls  154   a ,  154   b  of 14°. This has been found to be particularly effective at producing an airflow which maintains a high level of momentum as it leaves the slot-like opening  160 . The angle between the walls  154   a ,  154   b  can be varied between 10° and 20° if desired but 14° has been found to be advantageous. 
     In the arrangement shown in  FIG. 7   a , an upstanding member  82  is located between the walls  154   a ,  154   b . This upstanding member  182  is arranged to brace the two walls  154   a ,  154   b  apart at precisely the correct distance required for the hand dryer. The upstanding member  182  is moulded integrally with the upper wall  154   a  and is brought into abutment with the lower wall  154   b  during the manufacturing process. The lower wall  154   b  can include special shapings (not shown) against which the upstanding member  182  abuts. 
     The upstanding member  182  is shaped, in cross-section, as shown in either of  FIGS. 7   b  and  7   c . Essentially, the cross-sectional area of the upstanding member  182  is tear-drop shaped, each side resembling the upper half of an aerofoil. This shape is designed to allow the airflow passing between the walls  154   a ,  154   b  to pass the upstanding members  182  with the minimal amount of turbulence being created in the airflow. Specifically, the upstanding member  182  has a rounded upstream end  182   a  and an elongated downstream end  182   b . The breadth of the upstanding member  182  can be varied, as can be seen from  FIGS. 7   b  and  7   c.    
     The upstanding member  182  is shaped so that, at the points where it meets or joins one of the walls  154   a ,  154   b , a smoothly curved blend is formed (see  FIG. 7   a ). This can be achieved during the moulding process. Also, the upstanding member  182  is positioned so that its downstream end  182   b  lies a predetermined distance from the slot-like opening  160 . In the embodiment shown, that predetermined distance is substantially 2.5 mm, but this could be varied up to 10 mm. 
     A plurality of upstanding members  182  can be positioned at intervals along each of the slot-like openings  60 ,  62  included in the hand dryer  10  described above. The preferred number of upstanding members  182  positioned along each of the slot-like openings  60 ,  62  is three. Each upstanding member  182  is positioned so that the distance between the downstream end of the upstanding member  182  and the slot-like opening  60 ,  62  is the same. 
     The hand dryer  10  described above operates in the following manner. When a user&#39;s hands are first inserted into the cavity  30  through the cavity entrance  32 , the sensors  64  detect the presence of the user&#39;s hands and send a signal to the motor to drive the fan  40 . The fan  40  is thus activated and air is drawn into the hand dryer  10  via the air inlet  44  at a rate of approximately 20 to 40 litres per second and preferably at a rate of least 25 to 27 litres per second, more preferably air is drawn into the hand dryer  10  at a rate of 31 to 35 litres per second. The air passes through the filter  46  and along the fan inlet  42  to the fan  40 . The airflow leaving the fan  40  is divided into two separate airflows; one passing along the front air duct  50  to the slot-like opening  60  and the other passing along the rear air duct  52  to the slot-like opening  62 . 
     As the airflow meets the upstanding members  182 , it divides so as to pass around the upstanding members  182  and subsequently rejoins once it has passed the downstream end of the respective upstanding member  182 . The airflow is then ejected from the slot-like openings  60 ,  62  in the form of very thin, stratified sheets of high velocity, high pressure air. As the airflows leave the slot-like openings  60 ,  62 , the air pressure is at least 15 kPa and preferably approximately 20 to 23 kPa. Furthermore, the speed of the airflow leaving the slot-like openings  60 ,  62  is at least 80 m/s and preferably at least 100 or 150 m/s, more preferably approximately 180 m/s. Because the size of the slot-like opening  62  located at the end of the rear duct  52  is greater than the size of the slot-like opening  60  located at the end of the front duct  50 , a larger volume of air is emitted from the duct  52  than from the duct  50 . This provides a greater mass of air for drying the backs of the user&#39;s hands which is advantageous. 
     The two thin sheets of stratified, high velocity, high pressure air are directed towards the surfaces of the user&#39;s hands which, during use, are inserted fully into the cavity  30  and are subsequently withdrawn from the cavity  30  via the cavity entrance  32 . As the user&#39;s hands pass into and out of the cavity  30 , the sheets of air blow any existing water off the user&#39;s hands. This is achieved reliably and effectively because of the high momentum of the air leaving the slot-like openings  60 ,  62 . 
     Each stratified sheet of air is directed towards the wall of the cavity  30  which is remote from the slot-like opening through which the respective sheet of air is emitted. Because the slot-like openings  60 ,  62  are also inclined towards the lowermost end of the cavity  30 , the emitted airflows are directed into the cavity  30 . This reduces the risk of turbulent air movement being felt by the user outside the casing, eg in the user&#39;s face. 
     It is envisaged that it will take only a small number of “passes” of the hand dryer described above to dry a user&#39;s hands to a satisfactory degree. (By “pass”, we mean a single insertion of the hands into the cavity and subsequent removal therefrom at a speed which is not unacceptable to an average user. We envisage that a single pass will have a duration of no more than 3 seconds.) The momentum achieved by the airflows is sufficient to remove the majority of water found on the surface of the user&#39;s hands after washing during a single pass. 
     The water removed by the airflows is collected inside the cavity  30 . Each airflow will rapidly lose its momentum once it has passed the user&#39;s hands and the water droplets will fall to the lower end of the cavity  30  under the forces of gravity whilst the air exits the cavity  30  either through the cavity entrance  32  or via the open sides of the cavity  30 . The water, however, is collected by the drain  38  and passed to a reservoir (not shown) where it is collected for disposal. The reservoir can be emptied manually if desired. Alternatively, the hand dryer  10  can incorporate some form of water dispersal system including, for example, a heater for evaporating the collected water into the atmosphere. The means by which the collected water is dispersed does not form part of the present invention. 
     In an alternative embodiment, the slot-like openings  60 ,  62  can be arranged so that the sheets of air which are emitted therefrom are directed generally along planes which are substantially parallel to one another. This minimises the amount of turbulent flow present inside the cavity  30  whilst the drying apparatus is in use. 
     In a further alternative embodiment shown in  FIGS. 8   a  and  8   b  the slot-like openings are not of constant width across the length L of the cavity of the hand dryer.  FIG. 8   a  shows a plan view of the cavity entrance of length L. The dotted lines indicate the position and shape of the user&#39;s hands as they are normally inserted into the cavity  30  between the front and rear edges  32   a ,  32   b . The arrows  80  shown in  FIG. 8   a  indicate the direction of the airflow emitted from the slot-like openings  60 ,  62  located in the edges  32   a ,  32   b  of the cavity entrance  32 . In this embodiment the curved portions  33  of the rear edge  32   b  are symmetrical about the centre line A-A of the cavity entrance  32  with the centre portion of the rear edge  32   b  being closer to the front edge  32   a  at the centre line than at a position spaced from the centre line. The minimum distance d between the front and rear edges  32   a ,  32   b  is at the centre line. The distance between the front edge  32   a  and the rear edge  32   b  is at a maximum, D, at the mid point of each curved portion.  FIG. 8   b  shows the shape of the slot-like opening located in the rear wall of the cavity. 
     Preferably, the width of the slot-like opening in the rear wall varies gradually, increasing towards the mid point of the opening, at centre line A-A of cavity entrance  32 . 
     In this alternative embodiment it is preferred that the variation in width of the opening is achieved by varying the distance of the upper wall of the slot-like opening away from the lower wall, in the shape of a curve, preferably in a smoothly curving shape. More preferably the curve is symmetrical about centre line A-A of the cavity entrance  32 . Preferably the maximum width R of the opening is at centre line A-A and is 0.7 mm. 
     Preferably, the width r is substantially constant in regions F and G with the varying width region (region E in  FIGS. 8   a  and  8   b ) comprising at least half the total length L of the cavity entrance, most preferably the central half. Preferably r is 0.4 mm. 
     In region E of the hand dryer the width of the slot-like opening  62  is greater than the width of the slot-like opening  62  in regions F and G. The increase in size of the slot-like opening  62  provides a greater mass of air  80  from rear duct  52  for drying the backs of the user&#39;s hands in the thumb and forefinger area which is advantageous. The greater mass of air in region E and the momentum achieved by the airflow is sufficient to remove the majority of water found on the backs of the user&#39;s hands after washing during a single pass. 
     Because of the fact that the walls of the slot-like openings  60 ,  62  are able to be moulded by compression moulding of a thermosetting plastics material such as melamine, the manufacturing costs of the hand dryer are reduced in comparison to known apparatus. The presence of the upstanding members allows the width of the slot-like openings to be maintained at a constant value which ensures that the airflows emitted from the slot-like openings are substantially even along their length. 
     The invention is not intended to be limited to the precise detail of the embodiment described above. Modifications and variations to the detail which do not alter the scope of the invention will be apparent to a skilled reader. For example, the shape of the slot-like openings described above can be altered if desired. Also, the means by which the water removed from the user&#39;s hands is disposed of may be altered without departing from the essence of the present invention.