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.
1. Field of the Invention
The invention relates to a mechanical seal, in particular between an electric drive and a fluid pump used, for example, in dishwashers.
2. Prior Art
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The invention is described in greater detail below with reference to the drawing, in which:
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.
The illustration according to
The illustration according to
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.
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.
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
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.
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.
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.
Number | Date | Country | Kind |
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10 2006 062 523.4 | Dec 2006 | DE | national |
Number | Date | Country | |
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60907160 | Mar 2007 | US |