Abstract:
The invention relates to a towel dispenser ( 10 ) such as a paper towel dispenser comprising a housing ( 12 ) in which a paper roll and an issuing device ( 50 ) are arranged. Said issuing device can AC be controlled by a sensor ( 38 ). In order to simplify the operation and to increase the reliability of the towel dispenser, the invention provides that the sensor ( 38 ) is configured as a capacitive sensor.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a towel dispenser, in particular a paper towel dispenser, comprising a housing in which a receiver such as a roller for the towel or several towels and an issuing device for said towel(s) is provided, with the issuing device being actuatable by a sensor activatable from the housing exterior. The invention further relates to a towel dispenser, in particular a paper towel dispenser, comprising a housing in which on the one hand the dispensed product, such as a paper roll, and on the other hand an issuing device are arranged. 
     Towel dispensers, in particular paper towel dispensers, whose issuing device reacts to a light-sensitive sensor are known. To prevent the sensor from reacting to light changes as caused by persons walking past, for example, the sensor in the known dispensing devices must be arranged on a lateral housing panel so that defined light conditions are assured. This however entails the drawback that persons wishing to operate the towel dispenser only find the laterally arranged sensor after a lengthy search. Also, these types of dispensing devices are often arranged with insufficient clearance from side walls, so that the amount of light is insufficient to dependably trigger operation. 
     A paper towel dispenser is described in U.S. Pat. No. 4,406,421. From its housing exterior, a lever is accessible via which rack and pinion inside the housing mesh such that a section of the paper towel is accessible via a issuing opening. 
     WO97/29671 describes an electrically actuatable paper towel dispenser that can be actuated by means of a photographic sensor. 
     In order to obtain liquid soap from a dispenser, in particular in the area of operating theaters, without the need to directly touch the dispenser, a capacitive sensor is used in accordance with DE 34 00 575 A1, the one electrode of which runs directly in the area of the liquid dispensing opening. The counter-electrode is formed by the space on which the person wishing to use the dispenser is standing. 
     The problem underlying the present invention is to develop a dispensing device of the type mentioned at the outset such that its operation is simplified and its dependability increased. 
     SUMMARY OF THE INVENTION 
     The problem is solved in accordance with the invention substantially in that the sensor is a capacitive sensor with a first two-dimensional and a second two-dimensional electrode arranged inside the housing and passing along at least one housing panel. In particular, it is provided that the first and the second electrode run in one plane or in two planes that are parallel or approximately parallel to a housing panel, in particular to the housing front panel. The electrodes should here have diverging two-dimensional extensions, in particular in the ratio of 1:5 to 1:20, in particular 1:10. Here an electrode can have a surface area of, for example, 8 cm 2  and the other electrode a surface area of 0.8 cm 2 . 
     In particular, it is provided that the electrodes are at a distance from one another that in its width extension is equal to or less than the narrower electrode, which can also be described as strip-like. The electrodes themselves should have in the idle state, i.e. when the only dielectric outside the housing is air, a capacitance of approximately 1 pF±0.25 pF. If the dielectric then changes because a hand approaches, the change in capacitance will trigger a signal that in its turn actuates the towel dispenser. The electrodes forming the capacitor and running in one plane or if necessary in two parallel planes, i.e. offset to one another, generate a virtually rectified field such that the capacitance is affected whenever a change is made in the dielectric distance up to approximately 30 mm from the surface of the towel dispenser housing by, for example, the approach of a hand. The capacitor formed by the electrodes running in one plane can be described as a folded-up panel-type capacitor. 
     The capacitive sensor generates in its surroundings an electrical field that is changed by the approach of a hand. The change is evaluated and triggers a pulse for actuating the issuing device. The dispensing device can therefore be used regardless of room-related light conditions or other environmental effects. 
     Also, for operating the issuing device it is only necessary for the electrical field running between the electrodes to be changed in some way to the necessary extent, for example by an approaching hand, without the need for contact with the housing at a certain spot or for the hand to remain in a certain area. Functioning is also assured in rooms in which heavy soiling or high relative humidity occurs. 
     In a particularly preferred embodiment, it is provided that the sensor on the housing front side is arranged directly behind a front side of the housing. The arrangement of the sensor on the front ensures easy operation of the dispensing device. 
     An arrangement on a different side or the alignment of one electrode each on a separate housing side is also possible, provided an effective and influencable field extends outside the housing. 
     In a further preferred embodiment of the dispensing device, it is provided that the front side of the housing has at least one visual element indicating a sensor field and/or a removal opening. It is provided here that the visual element on the front side of the housing is designed as at least two recesses running horizontally. The recesses are preferably designed as semicircular and relief-like grooves. It is also provided that the recesses divide the front of the housing in the ratio of the golden section. 
     Apart from indicating the removal opening or localizing the sensor field or sensor surface, the recesses increase the stiffness of the housing surface. 
     To rule out malfunctions of the dispensing device, the sensitivity of the capacitive sensor can be adjusted. For the simplest possible design of the sensor, it is proposed that it has a first and preferably two-dimensional electrode and a counter-electrode, both of which are arranged directly behind a front surface of the front side in order to generate an electrical field outside the housing. 
     To ensure a mains-independent operation of the dispensing device, the latter is equipped with a battery-powered drive device. 
     For simple maintenance and operation, a switch is arranged on the inside of the housing, using which the issuing device can be controlled when the housing is opened. Furthermore, a timer element is provided using which the operation time of the issuing device can be adjusted. 
     An integrated time-lag element is also provided to determine a time after which the issuing device can be operated again. As an overload protection for a motor operating the issuing device, the circuit array has an overcurrent protection. 
     In a mechanical embodiment of the dispensing device, a spring-loaded lever arm that can be operated from the front of the housing is provided that has a rack for operating the issuing device. The rack here follows a circular path at whose centerpoint is the rotary axis of the lever. 
     For the issue of paper towels in the form of paper rolls, but also in the form of single towels, it is provided that the issuing device comprises a puller roller and a pusher roller arranged opposite thereto, with the rack interacting with a gear arranged on the shaft of the puller roller. Here the gear is designed with sleeve freewheel. 
     In the electrical embodiment of the issuing device, a motor with an associated transmission is provided that engages in the gear arranged on the shaft of the puller roller. The motor is here controlled by the sensor-operated control unit. 
     In particular, with an embodiment as a paper towel dispenser, with the paper towels being rolled off a paper roll, a tear-off device is provided, the latter being arranged on the inside of the housing and not being accessible from the outside. In this the embodiment in accordance with the invention differs from the prior art, as in known devices the tear-off device is arranged on the front side of the housing, so that injuries are possible when pulling out or tearing off the paper towels. 
     Regardless of whether the dispensing device is operated electrically or mechanically, the housing has a number of advantages over the prior art. In a particularly preferred embodiment, it is provided that an upper side of the housing is angled about 8° from the horizontal towards the beholder, so that rolling objects such as cigarettes cannot be rested on it. 
     Also, an intermediate field is provided between the upper side and the front side and angled towards the mounting wall. In addition, housing vision panels are arranged on at least one side wall for observing the items being dispensed. The housing is preferably made totally of plastic. 
     Further details, advantages and features of the invention are shown not only in the claims and in the features they contain—singly and/or in combination—but also in the following description of preferred embodiments shown in the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawing, 
     FIG. 1 shows a perspective view of a towel dispenser, 
     FIG. 2 shows a sectional view of the dispensing device in accordance with FIG. 1 in the electrical embodiment, 
     FIG. 3 shows a block diagram of a control circuit for the dispensing device in accordance with FIG. 2, 
     FIG. 4 shows a sectional view of the dispensing device in accordance with FIG. 1 in a mechanical embodiment, and 
     FIG. 5 shows a plan view of electrodes of a capacitive sensor. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a perspective view of a sensor-operated electrical dispensing device  10  in the form of a paper towel dispenser with integrated paper roll. 
     The dispensing device  10  has a housing  12  comprising a hood-like cover  14  and a rear panel  16  attachable to a mounting wall (not shown). The cover  14  is rotatably fastened to the rear panel  16 . 
     The hood-like cover  14  comprises an upper side  18 , a front side  20 , a lower side  22  and side surfaces  24 ,  26 . Overall the surface of the hood-like cover  14  is closed, smooth and glossy, with the individual sides  18 ,  20 ,  22  being at different angles relative to one another, so that a characteristic and dynamic appearance is obtained. 
     In particular, the upper side  18  is slightly inclined towards the beholder at an angle of preferably about 8°, so that the placing or leaving of objects such as cigarettes and other rolling objects is prevented. A transitional area  28  or intermediate field is provided between the upper side  18  and the front side  20  and is inclined towards the mounting wall so that the optical appearance of the hood-like cover  14  is matched to a removal opening  30  for towel removal arranged in the lower part of the front side  20 . 
     The housing  12  shown in FIG. 1 is a housing for an electrically operated dispensing device with sensor activation. For visual indication of the removal opening  30  and for localization of a sensor field  31 , two horizontally running recesses  32 ,  34  are provided in the front side  20  of the cover  14 . These are semicircular and relief-like grooves which divide the dispenser housing  12  in the golden section, so that a balanced appearance is obtained. The recesses  32 ,  34  designed as grooves of semicircular cross-section have a radius selected such that a flawless cleaning of the housing surface is assured. In addition to the informative character of the recesses  32 ,  34  such as grooves, they also increase the component rigidity, in particular of the front side  20 . 
     To prevent a direct view into the removal opening  30 , a housing surface section  36  in which the removal opening  30  has been provided is also inclined towards the mounting wall (not shown). 
     In both side panels  24 ,  26  of the hood-like cover  14 , vision windows  37  are provided to permit a check on how many unused towels are present in the housing  12  by means of a notional arrow shape. The vision windows are made of transparent plastic and are in two parts (erosion-type texture/without texture), with a check mark to simulate the contour of the towel supply, such as the paper roll. 
     The rear panel  16  is completely enclosed by the hood-like cover  14 , so that it is not visible in the mounted state. An all-round rim (not shown) on a rear side of the dispenser ensures a spacing of approx. 2.5 mm from the mounting wall, so that splash water, condensation etc. can run off unhindered and not get inside the dispenser  10 . 
     FIG. 2 shows a cross-section through the electrically operated dispensing device  10  in accordance with FIG.  1 . Compared with conventional dispensing devices, the dispensing device  10  in accordance with the invention is distinguished in that it has a capacitive sensor  38 , which in the embodiment is arranged directly behind the front side  20 . In particular, the capacitive sensor  38  has a two-dimensional electrode  40  and a counter-electrode  42  arranged behind a sensor field  31  that is particularly emphasized by the horizontally running grooves  32  and  34  on the front side. The arrangement of the capacitive sensor  38  on the front side permits considerably more user-friendly handling compared with dispensing devices known from the prior art, since the sensor does not necessarily have to be arranged on the side. 
     The electrodes  40 ,  42  run parallel or approximately parallel to the sensor field  31  at least in some areas. The sensor field  31  can cover the entire width of the housing. 
     Also, the sensor field can be in the area of the abutting front and side surfaces  20 ,  26  of the housing  10 , and in the area of an edge of the housing  10 . 
     The capacitive sensor  38  is connected to an evaluation circuit arranged on a PCB  44 , as described in detail for FIG.  3 . 
     A holder  46  extending from the rear panel  16  is provided and supports a roller  48  for receiving a towel roll, in particular a paper roll (not shown). For dispensing a section of the roll from the removal opening  30 , an issuing device  50  is provided. 
     The issuing device  50  comprises a puller roller  54  arranged on a shaft  52  and opposite which a pusher roller  58  is arranged, also on a shaft  56 . In a gap  60  formed between the puller roller  54  and the pusher roller  58 , a paper strip to be conveyed (not shown) is inserted, and is passed to the outside through the removal opening  30  during operation of the puller roller  54 . 
     For separation of the paper, a cutting edge  62  is provided that in the embodiment shown here is designed as a ZFN shaped angular section of sheet metal with a toothed pattern. The teeth provided on a longitudinal edge  63  of the cutting edge are preferably designed with differing lengths. 
     The transported paper strip is passed along an arc-shaped guide surface  34  in the direction of the removal opening  30 . 
     In the embodiment shown here in accordance with FIG. 2, a torque is transmitted by means of a motor  66  that can be actuated using the electric actuation device  44 . The motor  66  has on the output side a gear  68  that interacts via a further gear  70  with a gear  72  arranged on the shaft  52  of the puller roller  54 . 
     Furthermore, a power supply unit  74  is provided that can be designed both battery-powered and mains-powered. 
     In connection with the arrangement of the cutting edge  62  or tear-off edge, it must be noted that the latter is arranged on the inside of the housing, so that if anyone reaches into the removal opening  30  contact with the cutting edge  62  is ruled out or at least largely ruled out. 
     FIG. 3 shows a block diagram of a sensor-controlled motor control unit  76 . The motor control unit  76  has a power supply unit  78  with a transformer  80  and a first supply unit  82  for power supply to the sensor  38  and a second supply unit  84  for power supply to the motor  66 . 
     The capacitive sensor  38  comprises the first two-dimensional electrode  40  and the counter-electrode  42  for generation of an electrical field. The sensor  38  is connected to an electronic control unit  88  which is in turn connected to a motor control circuit  90  that receives its energy from the second supply unit  84 . 
     The electronic control unit  88  is furthermore connected to a trimmer  92  used for setting the actuation time of the motor  66 , which directly determines the paper length. Furthermore, a switch  94  is provided that permits manual actuation of the motor  66  when the cover  14  is opened to change the paper. Overall, actuation of the motor  66  is only possible when the cover  14  is closed. The closed position of the housing or hood-like cover  14  is picked up by a switch  96 . 
     The motor control  90  directly controls the motor  66 , which actuates the issuing device  50  via a transmission having the gears  68 ,  70 . Concerning the operating mode of the motor control unit  76 , it must be noted that the approach of a hand changes the electrical field formed between the electrodes  40  and  42 , in particular the dielectric constant of the dielectric otherwise formed by air, and that the change is registered by the electronic control unit  88  and processed into a control signal. Depending on the actuation time set using the trimmer  92 , the motor  66  is operated for a certain period so that a paper strip of predetermined length is dispensed. 
     All components of the control circuit  76  are designed with SMD technology. Also, the complete circuit including the electrodes  40 ,  42  is arranged on a PCB. It must be mentioned that it is particularly advantageous for the PCB  44  and the electrodes  40  and  42  to be arranged inside the housing  12  and hence to be neither visible nor accessible from the outside. Also, the control circuit  76  can be arranged with the electrodes  40 ,  42  in a separate housing, thus providing additional protection and, in the case of a fault, easy maintenance; for example, in the case of a fault in the electronic circuit the housing has only to be removed and then replaced by a new and correctly functioning unit. 
     To provide a dispensing preventer to stop repeated operation, an integrated time-lag element is provided, with the time lag also being adjustable using a trimmer. Furthermore, an overcurrent protection circuit is provided so that when the motor is blocked, for example by a paper jam or clogging, the electronic unit is protected against excessive current. 
     As shown in FIG. 5, the electrodes  40 ,  42  are designed approximately rectangular and have surface ratios of preferably 1:10. For example, one of the electrodes—in the embodiment the electrode  40 —can have a surface area of 8 cm 2  and the other electrode  42  a surface area of 0.8 cm 2 . The capacitor formed by the electrodes  40 ,  42  should then have—when the dielectric is not influenced by a hand for example, i.e. is in the idle state—a capacitance of approximately 1 pF±0.25 pF. If there is then a change in the dielectric, for example by a hand approaching the housing  12  and in particular the sensor field  31 , a change in the capacitance results from the change in the dielectric and triggers a switching operation for dispensing a section of towel, in particular a paper towel, pulled off a roll. 
     As FIG. 5 already makes clear without a detailed description, the electrode  40  is rectangular and the electrode  42  is of strip-like form, said electrodes  40 ,  42  having a spacing  41  that is narrower than the electrode  42 . If a surface of a unit  1  is bounded by the electrodes  40 ,  42  including the spacing  41 , the electrode  40  takes up about 80% of this area, the strip-like spacing  41  about 5% and the strip-like electrode  42  about 15%. As a result the required rectified electrical field extending to the outside of the housing  12  is generated. 
     By the design of the electrodes  40 ,  42 , in particular of their different sizes and arrangement in a plane running parallel to a housing panel, in particular to the front housing side  20  or to the sensor surface  31 , a rectified electrical field extending to the housing exterior is generated and is effective to the required extent for triggering a control command whenever a hand for example moves into the area up to 30 mm from the front side  20  or sensor surface  31 , without the need for directly touching the front side  20  or the sensor surface  31 . 
     FIG. 4 shows a sectional view of a mechanically actuatable dispensing device  100 . It must be noted here that the form of the housing  12  corresponds mainly to the form of the electrically operated dispenser  10 . In particular, the same issuing device  50  is used as already described with reference to FIG.  2 . 
     In accordance with the invention, a lever arm  102  is provided for mechanical actuation of the issuing device  50  and is pivotably mounted in the inside of the housing  12  on an axis  104 . On the outside of the housing a handle  106  is provided that is connected to the lever arm  102  and is movable substantially parallel to a surface  108  on the front side  20  of the housing  12  for operation of the lever arm  102 . For vertical movement of the lever arm  102 , a slot-like and substantially vertical opening  110  is provided in the front side  20 . 
     One end  112  of the lever arm  102  opposite the axis  104  is provided with a rack  114  following an arc-shaped path, with the arc-shaped rack  114  interacting with the gear  72  arranged on the shaft  52  and exerting a torque on the puller roller  54  when the lever arm  102  is actuated. The return of the lever arm  102  to its original position is achieved using a spring  116 , which is for example designed as a torsion spring and is arranged coaxially to the axis. It is provided here that the gear  72  is designed with sleeve freewheel, so that no torque is transmitted by the freewheel movement to the puller roller  54  in the event of an upward movement of the lever arm or curved rack  114 . 
     With the teachings in accordance with the invention, easy-to-operate and fault-resistant towel dispensers are provided, and the servicing costs are reduced by easy maintenance and the use of only a few elements subject to wear. The design in accordance with the invention also permits simple conversion from mechanically to electrically operating paper dispensers and vice versa. 
     The housing  12  is preferably made of an impact-resistant and corrosion-resistant plastic whose stability is increased by edging and beading. The provision of an internal sensor in accordance with the invention means than external and fault-prone sensors can be dispensed with.