Level control arrangement for dishwashers

Abstract: This invention relates to a level control arrangement for a dishwasher. The dishwasher comprises a tub (10) in which the dish is placed and in which liquid is circulated by means of a circulation pump (27) which via a tube shaped connection (26) communicates with an inlet (25) which is placed in the lower part of a chamber (23) situated at the bottom of the tub. The chamber is at least partly separated from the tub by means of a filter (20) or the like and comprises also a heating source (31) for warming up the liquid. The connection (26), in addition to said inlet (25), has an opening (32) which at least partly is placed above or at the same level as the heat emitting parts of the heating source (31). The opening (32) has such a shape and size that the surface exposed to the chamber increases when the liquid level in the chamber sinks.

Description: This invention relates to an arrangement for a dishwasher comprising a tub in which the dish is placed and in which liquid is circulated by means of a circulation pump which via a tube shaped connection communicates with an inlet which is placed in the lower part of a chamber situated at the bottom of the tub, the chamber at least partly being separated from the tub by means of a filter or the like said chamber also comprising a heating source for warming up the liquid, the connection in addition to said inlet having an opening which at least partly is placed above or at the same level as the heat emitting parts of the heating source. The purpose of said arrangement, which is described in DE 2 412 257, is to prevent the liquid surface from sinking to unacceptable levels. If the surface sinks below the heating source this means that the heating source and perhaps also the bottom of the chamber will not be covered by cooling liquid any longer resulting in overheating of the heating source and in case the bottom consists of plastic also in deformation of the bottom. By providing the inlet channel of the pump with an air inlet which is placed at a horizontal higher level than the heating source a sudden air flow into the pump is achieved when the flow of liquid to the chamber has been reduced i.e. when the filter has been clogged. This means that the pressure drops rapidly and activates a pressure sensor who disconnects the heating source. The arrangement has the drawback that the heating process is cut off which means bad dishwashing result. The purpose of the present invention is to eliminate the abovementioned drawback and to create an arrangement where the liquid level and hence the spray pressure is controlled with respect to the degree of filter clogging at the same time as the electric supply to the heating source is maintained so that the dishwashing procedure can be completed. This is achieved by means of an arrangement having the characteristics given in the claims. An embodiment of the invention will now be described with reference to accompanying drawings where Fig. 1 shows a vertical sectiont through a dishwasher according to invention whereas Fig. 2 in a exploded view shows the lower part of the tub and Fig. 3 is a vertical section through a suction part forming a tube-shaped connection of the dishwasher. As appears from Fig. 1 the dishwasher comprises a tub having side walls 11 a rear wall 12, a roof part 13 and a bottom 14. Moreover there is a door, not shown, which normally covers the front wall. One or several baskets 15 with dish can be inserted into the tub. The bottom of the dishwasher is inclined downwards to a collecting container 16 which is shaped as pan a part of the container forming a sump 17 in which the inlet 18 to a drain pump 19 is placed. The container 16 is covered by a fine sieve 20 and a coarse sieve 21 which both can be lifted from the container for cleaning. The fine sieve 20 covers the upper part of the container and also forms a partition wall 22 in the container so that a chamber 23 is created. This chamber communicates, via an inlet opening 25 adjacent the bottom of the chamber and a tube shaped connection 26, with the suction side of a circulation pump 27 having an outlet connected to a pipe 28 which is centrally placed in the dishwasher and on which a spray arm 29 with nozzles 30 is placed for rotating motion. The chamber 23 also encloses a heating source 31 in the form of an electric coil or the like extending horisontaly from one of the walls of the chamber. The connection 26, the lower part of which is provided with the downwardly extending comparatively large inlet opening 25 and the upper end of which communicates with the circulation pump, has a slot-shaped, curved opening 32 facing towards the chamber and being placed somewhat above the upper heat emitting part of the heating source 31 which means that the surface of the opening 32 exposed to the chamber above the liquid level increases when the liquid level sinks. The arrangement operates in the following way. During the circulation cycle the liquid flowing out from the nozzles 30 is collected at the bottom of the tub and is directed towards the container 16 and flows through and on the fine sieve 20 and the coarse sieve 21 into the chamber 23 from which the liquid is sucked out by means of the circulation pump 27 and is delivered to the rotating disharm 29. During the dishwashing cycle the liquid level in the chamber 23 is normally situated above the heating source. Should however the fine sieve 20 become so clogged that the liquid level in the chamber 23 sinks because the capacity of the circulation pump 27 exceeds the incoming flow the opening 32 will successively be uncovered which means that the circulation pump will suck more and more air and gradually reduce the flow of water to the pump resulting in a balanced water level. Thus a simple selfcontrolled flow through the pump is achieved at the same time as the electric supply to the heating source is maintained which means that the dishwashing cycle is completed although with reduced spray pressure. Usually the filter is cleaned during such a process since the hot water dis-solves the particles which are clogged in the filter. It should be observed that when the water surface reaches a predetermined minimum level corresponding to the level of the heating source, which would be the case if the filter is totally blocked, the electric supply to the heating source has to be cut off. This can easily be effected by setting the pressure sensing means in the circulation circuit for the water at such a value that the electric supply to the heating source is disconnected when this pressure drops too much.

Claims: Arrangement for a dishwasher comprising a tub (10) in which the dish is placed and in which liquid is circulated by means of a circulation pump (27) which via a tube shaped connection (26) communicates with an inlet (25) which is placed in the lower part of a chamber (23) situated at the bottom of the tub, the chamber at least partly being separated from the tub by means of a filter (20) or the like said chamber also comprising a heating source (31) for warming up the liquid, the connection (26) in addition to said inlet (25) having an opening (32) which at least partly is placed above or at the same level as the heat emitting parts of the heating source, characterized in that - between a certain level interval - the part of the opening (32) which is not covered by the liquid gradually increases when the liquid level in the chamber sinks. Arrangement according to claim 1, characterized in that the connection (26) extends upwards to the pump from the lower part of the chamber. Arrangement according to any of the preceding claims, characterized in that the opening (32) is slot-shaped.

Inventors: LAGERSTRAND DAN EVERT, LAGERSTRAND, DAN EVERT
Applicants: ELECTROLUX AB, AKTIEBOLAGET ELECTROLUX
Application year: 1990
Main classification: A47L15
IPC codes: A47L15