Abstract:
The invention relates to an apparatus for identifying a leak in a mechanical seal separating the side of a conveyor unit which is in contact with a medium from an electric drive which is arranged outside the medium. If there is a leak, the escaping medium is detected by a sensor element which is arranged in a hollow space, which is bounded by a removable component, and serves to identify escaping medium.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on German Patent Application No. 10 2006 062 523.4 filed 29 Dec. 2006, upon which priority is claimed, and on Provisional Application 60/907,160 filed on Mar. 23, 2007. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a mechanical seal, in particular between an electric drive and a fluid pump used, for example, in dishwashers. 
         [0004]    2. Prior Art 
         [0005]    DE 33 04 097 A1 relates to a single-action mechanical seal comprising a connection ring which is fixed to a rotating machine part and has a first annular sliding surface, and also a non-rotating sealing ring which is supported on a stationary machine part and has a second annular sliding surface which bears against the sliding surface of the stop ring during operation. The sliding surface of the sealing ring has at least one weakened section which is weaker than the rest of the sliding surface. The sealing ring contains a closed channel which is separated from the sliding surface by the abovementioned weakened section and is connected to a leak detector which reacts in response to the action of the liquid to be compressed. 
         [0006]    DE 33 42 297 C2 relates to an apparatus for sealing off a bearing, which is lubricated with lubricant, of a drive shaft of ships or floating platforms or the like. The apparatus is equipped with a mechanical seal on the water side and with a pair of lip seals with sealing lips which face each other on the lubricant side. A leak space is made between the mechanical seal and the outer lip seal, and a lubricant chamber is formed between the lip seals. The leak space is connected via a leak line to an elevated leak liquid container which is provided with a ventilation pipe, and the lubricant chamber is connected by a lubricant line to an elevated lubricant container which is provided with a ventilation pipe. The elevated lubricant container is mounted above the elevated leak liquid container. The lubricant chamber contains at least one further lip seal, with a sealing lip which is directed toward the rear, between the rear lip seal and the issuing point of the lubricant line into the lubricant chamber. The lubricant supply apparatuses are connected to the lubricant line and increase the lubricant pressure in the lubricant line to approximately half the external water pressure at the water depth at which the drive device is normally located, when the pressure in the leak space rises above the normal value. 
         [0007]    DE 197 24 308 A1 and EP 0 886 088 B1 relate to a diagnostic system for a mechanical seal, and disclose a method for determining the likelihood of failure and/or the theoretical residual service life of a mechanical seal, in which method the pressure of the medium, the leakage pressure, the moisture on that side of the mechanical seal which is averted from the medium, and also the temperature of the medium and/or the temperature of elements of the mechanical seal are measured. The measured values are compared with known comparison values, and the likelihood of failure and/or the remaining residual service life of the components are/is calculated from the deviation between the measured values and the known comparison values. 
         [0008]    The apparatuses or methods known from the cited prior art permit only a rough estimation of the likelihood of failure of mechanical seals. Mechanical seals which are used, for example, in dishwashers, in particular on the flange between an electric drive and a pump which circulates wash fluid, are parts which are subject to wear and on which great demands are placed during long term operation of such systems and machines. On account of the unavoidable wear during the operating time, exchange deadlines by which the mechanical seals should be replaced, even if they appear to still be intact, are set at regular cyclical intervals. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is based on the object of providing a mechanical seal which firstly can be monitored in the long term and secondly is very easily accessible for seal replacement. 
         [0010]    The solution proposed according to the invention is distinguished primarily by its simplicity. A conveyor unit which is, for example, arranged within a tank of a conveyor-type dishwasher is connected to an electric drive which is provided outside the tank, with the interposition of a flange. The usually annular flange is located on the outside of the tank in which the conveyor unit and the fluid which is circulated in the conveyor unit are contained. In accordance with the solution proposed according to the invention, an annular groove in which a sensor element is accommodated is provided on the end face of the flange, preferably on that face of the flange which faces a dome-like raised area. The sensor element is connected to the controller of the conveyor-type dishwasher via electrical contact lines. 
         [0011]    An annular groove which is bounded by a wall which bounds a hollow space is preferably made on the end face of the flange connection. The hollow space which is bounded by the wall and the end face of the flange is bounded by a removable covering ring. The covering ring contains a mechanical seal which has a movable sliding ring which can rotate in relation to a stationary sliding ring. 
         [0012]    The annular groove which is made in the end face of the flange between the conveyor unit and the electric drive accommodates at least one sensor element which has, for example, two sensor pins which are connected to a controller via an electrical line in each case. The at least one sensor element is admitted into the annular groove on the end face of the flange by means of an interlocking or force-fitting, preferably removable, fixing system. 
         [0013]    If the mechanical seal by means of which the conveyor unit, which is, for example, arranged in the tank of a treatment zone of the conveyor-type dishwasher, is sealed off from the tank base and the electric drive springs a leak, as may occur after an operating time of several hundred hours, water from the inside of the tank in which the conveyor unit is located enters the hollow space within the flange by means of the mechanical seal along the casing surface of the drive shaft on which the mechanical seal is accommodated. During rotation of the drive shaft of the electric drive, the water which enters is thrown against the wall, which bounds the hollow space, of the flange on account of the action of centrifugal forces and runs into the wall along the base surface of the hollow space. The water entering the hollow space collects in the annular groove on the end face of the flange in which the at least one sensor element is immersed. The hollow space is closed by the removable covering ring which can be easily removed from the flange—after removal of the conveyor unit from the tank—, so that the hollow space in which the water collects if there is a leak in the mechanical seal is easily accessible. An indication that the mechanical seal has failed or that complete breakdown of this component is imminent can be released to the machine control system by the at least one sensor element which is admitted into the annular groove on the end face of the flange in the hollow space. Each flange of each tank of the conveyor-type dishwasher, which may have a plurality of treatment zones which are connected in series, is preferably provided with at least one such sensor element, so that it is possible to indicate in the machine control system or in a display which is connected to the machine control system which mechanical seal in which tank in which treatment zone has failed or is just about to break down completely. 
         [0014]    The at least one sensor element which is mounted in the flange within the hollow space with a removable covering ring is preferably connected to the machine control system of the conveyor-type dishwasher. The part of the mechanical seal which has failed can be easily removed on account of the covering ring which can be removed from the flange between the conveyor unit and the electric drive, and be repaired outside the machine. The covering ring which can be removed from the flange also makes it possible to dry the base of the hollow space within the flange, in which the groove is in the form of, for example, an annular groove, and therefore to remove from the hollow space all the water which has entered said hollow space. The removable covering ring can then be mounted on the flange again. This provides significantly better accessibility to the annular groove and also the option of completely drying the hollow space in the end face of the flange. 
         [0015]    A central maintenance service for a region or country can continuously monitor the dishwasher using the machine control system, for example by connection of the machine control system to the Internet, so that, if necessary, a service technician with replacement parts can arrive in good time, in order to keep repair- and replacement-related downtimes of the dishwasher to a minimum. 
         [0016]    The connection lines which make electrical contact with the at least one sensor element in the annular groove of the flange are likewise insulated from the tank which contains the flange which seals off the inside of the tank, which contains the fluid to be circulated, from the outside. The solution proposed according to the invention can be used particularly in conveyor unit/electric drive configurations which are oriented in a vertically suspended manner in relation to the base surface of a tank of a treatment zone of the conveyor-type dishwasher. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention is described in greater detail below with reference to the drawing, in which: 
           [0018]      FIG. 1  shows a lateral section illustration of the flange with the tank base, conveyor unit, flange and electric drive which drives the conveyor unit illustrated in section, 
           [0019]      FIG. 2  a perspective section illustration of the unit comprising conveyor unit, flange and electric drive, accommodated on a dome-like raised area of the tank of a treatment zone of the dishwasher, 
           [0020]      FIG. 3  shows an illustration of the mechanical seal in the region of the tank base, and 
           [0021]      FIG. 4  shows a schematic illustration of a sensor element which can be inserted into the annular groove, and the connection of said sensor element to a controller with a display or a monitor. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    Embodiments of a conveyor dishwasher unit  10  which is driven by means of an electric drive  12  are described in the text which follows. The conveyor unit  10  is connected to the electric drive  12  by means of a flange  14 . The combination comprising conveyor unit  10  and electric drive  12  may be used in cleaning systems, for example conveyor-type dishwashers, be they belt- or rack-conveyor dishwashers, in domestic dishwashers, in commercially useable batch dishwashers or single-chamber dishwashers, in cleaning and disinfection devices for hospitals, residential homes for the elderly, or the like. 
         [0023]    The illustration according to  FIG. 1  shows that the conveyor unit  10  is connected to the electric drive  12  (which is schematically indicated here) by means of the flange  14 . A plurality of stud bolts  16  which support a housing  20  of the conveyor unit  10  are located on the flange. An output shaft  18  by means of which the conveyor unit  10  (not illustrated in any detail) is driven extends from the electric drive  12 . The conveyor unit  10  continuously or cyclically circulates a fluid, for example cleaning liquid or final-rinse liquid or the like, which is stored in a tank  26 . The housing  20  of the conveyor unit  10  comprises an intake opening  22  through which the output shaft  18  of the electric drive  12  extends. 
         [0024]    The illustration according to  FIG. 1  shows that the electric drive and the conveyor unit  10  are arranged by means of the flange  14  in a vertically suspended arrangement  50  in relation to a tank base  28  of the tank  26 . In order to accommodate the flange  14 , the tank base  28  of the tank  26  has a dome-like, preferably truncated cone-like, raised area  24 . The flange  14 , whose stud bolts  16  extend through the tank base  28  of the tank  26 , is mounted on the tank base  28  of the tank  26 . The electric drive  12  is located on the outer face  32  of the dome-like, preferably truncated cone-like, raised area  24 . 
         [0025]      FIG. 1  shows a hollow space  46  formed in the flange  14 . This hollow space  46  is bounded firstly by means of a removable covering ring  34  and secondly by means of the material of the flange  14  itself and finally by an end face  36  of the flange  14 . A groove  38  is formed on the end face  36  of the flange  14  such that it runs concentrically in relation to the axis of the electric drive  12  or of the output shaft  18 . The groove  38  is preferably designed as an annular groove and has a groove base. A mechanical seal  40  is located in the region of the removable covering ring  34 . The mechanical seal  40  comprises a rotating ring  42  and a stationary ring  44 . 
         [0026]    The hollow space  46  is closed by means of the removable covering ring  34 . The removable covering ring  34  can be fixed to the end face  36  of the flange  14  so as to close the hollow space  46 , for example by means of fixing screws  48  or other fixing elements. 
         [0027]    For the sake of completeness, reference is made to the fact that a pressure nozzle  22  is formed on the housing  20  of the conveyor unit  10  and the fluid which is to be circulated and is stored in the tank  26  is supplied to cleaning systems again by means of said pressure nozzle. 
         [0028]      FIG. 2  shows a perspective arrangement of the unit comprising conveyor unit, flange and electric drive which is arranged on the outside in relation to the tank. 
         [0029]      FIG. 2  shows that the dome-like, preferably truncated cone-like, raised area  24  is formed on the inner face  30  of the tank base  28  of the tank  26 . The housing  20  of the conveyor unit  10  sits on said raised area. 
         [0030]      FIG. 2  shows that the housing  20  of the conveyor unit  10  is accommodated in a ring system  54  on a centering dome  56  and is acted on by the fluid, which is to be circulated and is stored in the tank  26 , by means of the pressure nozzle  22 . The electric drive  12  is located on the outside  32  of the tank  26 . The perspective view of the unit comprising conveyor unit, flange and electric drive which is illustrated in  FIG. 2  shows that the groove  38  which is formed on the end face  36  of the flange  14  has a groove base  58 . The hollow space  46  is closed firstly by the end face  36  of the flange  14 , secondly by a wall  16  of the hollow space  46  and also by the removable covering ring  34 . The hollow space  46  contains the mechanical seal  40  which comprises the rotating ring  42  and the ring  44  which is accommodated in the covering ring  34  in a stationary manner. 
         [0031]      FIG. 2  also shows that the base of the housing  20  of the conveyor unit  10  is mounted on the stud bolts  16 , which each have a blind hole  64 , by means of screws  62 . If fixing elements  62  in the form of screws are used, the blind holes  64  in the stud bolts  16  can be provided with internal threaded sections. The fluid which is to be circulated and is stored in the tank  26  flows to the conveyor unit  10  via an opening  52  which is formed in the base of the housing  20  of the conveyor unit  10 . The fluid is circulated by this conveyor unit and leaves the housing  20  of the conveyor unit  10  by means of the pressure nozzle  22  and is conducted to a cleaning system (not illustrated) of a treatment zone of the conveyor-type dishwasher. 
         [0032]      FIG. 3  shows an illustration of the mechanical seal which is formed on the flange between the electric drive and the conveyor unit. The hollow space  46  is bounded by the hollow space wall  60  which at the same time serves as a run-off surface  70  for splash water. 
         [0033]      FIG. 3  also shows the mechanical seal  40  which comprises the rotating ring  42  and the stationary ring  44 , between which a sealing gap is formed. The illustration according to  FIG. 3  shows that the stationary ring  44  of the mechanical seal  40  is embedded in the stationary component covering ring  34  on account of the geometry of the covering ring  34 . The rotating ring  42  which interacts with the stationary ring  44  is connected to the output shaft  18 , which extends from the electric drive  12  through the flange  14  symmetrically to an axis  74 , in a stationary manner by means of a sealing element  66  which is in the form of a sleeve or folding bellows. The illustration according to  FIG. 3  further shows that the groove  38  runs in the end face  36  of the flange  14  and is bounded by the groove base  58 . The flange  14  is preferably in the form of a rotary part into whose end face  36  the groove  38  can be milled. The illustration according to  FIG. 3  shows that in this case the annular groove  38  is replenished with a reserve of water which has entered, in accordance with a water level  72 . At least one sensor element  76  (compare  FIG. 4 ), which is approximately in the form of an arc of a circle, is admitted into the groove  38  which is illustrated in  FIG. 3  and is formed in the end face  36  of the flange  14 . 
         [0034]    If the mechanical seal  40  is defective or wear occurs during operation on account of the constant friction between the rotating ring  42  and the stationary ring  44 , water from the housing  20  of the conveyor unit  10  continuously and constantly enters the hollow space  46 , which is closed by the removable covering ring  34  which is in the form of a stationary component, along a casing surface  68  of the output shaft  18 . On account of the rotation of the output shaft  18 , the water splashes against the hollow space wall  60  which bounds the hollow space  46  in the radial direction and at the same time functions as a run-off surface  70  for the splash water. The water which flows downward in the vertical direction from the hollow space wall  60  collects in the groove  38  in the end face  36  of the flange  14 . A rising water level  72  above the groove base  58  of the groove  38  can be detected by the sensor element  76  (compare the illustration according to  FIG. 4 ) which is accommodated in the groove  38 . On account of the solution proposed according to the invention, the ingress of water from the tank  26  into the hollow space  46  can be detected in the vertically suspended arrangement  50  of the conveyor unit  10  and the electric drive  12  in relation to the tank base surface  28 , which arrangement is illustrated in  FIG. 3  and moreover also in  FIGS. 1 and 2 . 
         [0035]      FIG. 4  schematically shows the at least one sensor element which is inserted into the groove which is formed, for example, on an end face of a flange. 
         [0036]    The sensor element  76  can be substantially in the form of an arc of a circle, for example as a 90° arc of a circle  82 . A first sensor pin  78  and a second sensor pin  80  extend through this arc of a circle  82 . The lengths by means of which the two sensor pins  78  and  80  protrude beyond the lower face of the arc of a circle  82  can be selected in accordance with the depth of the groove  38 , that is to say the distance between the lower face of the arc of a circle  82  and the groove base  58 , and are preferably designed such that the at least one sensor pin  78 ,  80  protrudes beyond the lower face of the arc of a circle  82  but does not stand on the groove base  58  but instead ends at a distance in front of it. 
         [0037]      FIG. 4  shows that contact is made with each of the two sensor pins  78  and  80  via connection lines  84 . The connection lines  84  which make contact with the ends of the sensor pins  78  and  80  on the upper face of the arc of a circle  82  are connected to the controller  86  at the other end. The controller  86  is, in turn, connected to a monitor, a display, a PC or the like via a data line  90 . Therefore, an indication or a warning or a replacement message can be output as soon as the water level  72  within the groove  38  exceeds a specific maximum level. The sensor element proposed according to the invention can detect both a continuous increase in the water level  82 , that is to say a gradual breakdown of the mechanical seal  40 , and also sudden failure of the mechanical seal in the event of water breaking into the hollow space  46 . The two sensor pins  78  and  80  are short-circuited by means of the water which collects above the groove base  58  in the annular groove  38 , and a corresponding signal is generated via the contact lines  84 , the signal being registered in the controller  86 . The corresponding signal can be, for example, displayed on a machine display of the conveyor-type dishwasher by means of the controller  86 , so that the operator is immediately informed as to the treatment zones of the conveyor-type dishwasher in which the mechanical seal provided there has failed. 
         [0038]    Failure of a mechanical seal  40  on account of a corresponding increase in the water level  72  on the base of the hollow space  46  can be detected by means of the at least one sensor element  76  and output to a monitor, a display or a PC via connection lines  84 , controller  86  and data line  90 , with the PC being situated, for example, in a service center. On account of this solution, a system can be installed by means of which a mechanical seal  40  which is in a state of total failure can be replaced ahead of schedule in a maintenance measure within the scope of preventative measures or secondly replacement of the defective mechanical seal  40  can be immediately initiated in an emergency. 
         [0039]    The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.