DISHWASHER TANK

Description

BACKGROUND TO THE INVENTION

A dishwasher has a tub for washing, rinsing and drying, either made of stainless steel or made of plastics material. This washing tub is generally fixed to a lower frame which forms the support for all of the power equipment necessary for the operation of the appliance (pumps, solenoid valves, filters, fluid channels, heating elements, etc.).

Generally this tub is produced in a single piece and is connected by through-holes to various pipes for the distribution, discharge and circulation of washing water, resulting in complicated assembly operations which can only be correctly carried out in the factory. All of this dictates the size of the appliance and thus the volume occupied by the appliance during the various phases of its transport and storage from its place of manufacture to the home of the user.

Moreover, for the purposes of a certain sobriety in terms of energy consumption, knowing that the energy consumption of a dishwasher is principally due (approximately 80%) to the heating of the washing water, research is being carried out on means for the recovery of heat from the washing liquor before it is drained from the tub. In the prior art there are documents which describe dishwashers in which a type of buffer tank is attached to one of the side walls of the tub so that this wall constitutes a heat exchanger between the tub and this tank. Thus the water which is contained in the tank and which originates from the softener is pre-heated for a washing operation or subsequent rinsing operation in the tub. This prior art is illustrated by the documents DE 80 19951 and DE 33 16716.

The subject of the invention is a dishwasher tub structure which makes it possible, on the one hand, to save a portion of the energy expended in heating the water and, on the other hand, to simplify the different assembly operations so that they can be carried out in situ at the home of the user, in particular in order to facilitate maintenance and troubleshooting, which are advantageous for reducing the obsolescence of the appliance, and even in order to be able to deliver the appliance in dismantled subassemblies to the user who can easily construct the appliance at home, with the advantage of a significant reduction in the volume of the appliance between its manufacture and its use.

SUBJECT OF THE INVENTION

To this end, the dishwasher tub according to the invention is in accordance with claim 1.

This arrangement has the advantage of enabling a pre-heating of the water, while it is waiting to be used, for a subsequent load of dishes or for the next phase of the washing cycle, while retaining the possibility of simple assembly in situ by a professional or even by a user.

One of the walls advantageously carries a level sensor of the water contained in the tank, which level sensor is arranged at a level which corresponds to a known fraction, for example half, of the total volume of the tank.

This sensor is also used as a sensor of the water resistivity which it monitors in order to be able to adjust the degree of hardness of the water which is delivered by the water network to the dishwasher. This function is provided in the appliances of the prior art, by a uniform pre-setting for all of the appliances in the factory. However, the hardness of the water is very variable from one water distribution network to another, and even in the same water network depending on the origin of the water supplied thereto.

In one particular embodiment, the walls of the tub are independent from one another, they are produced in molded plastics material and are assembled on the adjacent walls by means of centering devices for their relative positioning and by lever clamps exerting a pressure between two adjacent walls in the direction of their respective centering device in order to strengthen their support on one another and to compress a sealing gasket in the region of this support.

Further features and advantages will be found in the following description of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to the accompanying drawings, in which:

FIG. 1 is a sketch illustrating the overall structure of the tub of the dishwasher according to the invention,

FIG. 2 is a sketch of a variant of the three side walls of the tub according to the invention,

FIG. 3 is a simplified diagram of the hydraulic circuit of the machine according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, the bottom wall 2 of the tub, preferably made of plastics material, has been shown on a base 1 which forms in the known manner a support frame for various power elements of the appliance (pumps, valves, heating elements, etc.). This bottom wall is secured to this frame by any appropriate means, whether detachable or not.

The side walls of the tub which enclose the opening, are referenced 3 and 4. The back wall is referenced 5 and the top wall is referenced 6. Preferably, the five walls are independent and produced in molded plastics material.

Centering devices, such as at 7, have been provided at the base of the walls 3, 4 and 5 and below the edge 6a of the wall 6, which centering devices make it possible to ensure a correct positioning of the walls relative to one another by cooperating with housings 8 correspondingly provided in the edges of the walls 2, 3, 4 and 5. Centering devices, not shown, are also present in the region of the adjacent vertical edges of the walls 3, 4 and 5.

Lever clamps 9 make it possible to maintain the adjacent edges of the walls in tight abutment, in the manner of a clamp, in order to crush a seal, as referenced at 10, which ensures the sealing of the tub between the different walls. Naturally, the seals used in the invention are designed to bypass the centering devices which is not shown.

In FIG. 2, the walls 3, 4 and 5 are shown schematically and in partial section in order to illustrate the fact that they are hollow so as to form intermediate or buffer cavities 11, 12, 13 for water between the water inlet and the supply of the tub. These cavities communicate with one another by means of pipes (not shown) arranged in the frame and/or formed in, or carried below, the bottom wall of the tub and connecting the nozzles 14 of each cavity in series or in parallel to these pipes in order to form a single tank. It will be noted that the production of each wall from molded plastics material enables a simplified manufacture relative to a double metal wall or a tank attached to the external face of a steel tub wall. This embodiment also enables the thicknesses of the walls of the tank to be adjusted, the wall adjacent to the tub being able to be relatively thin in order to promote the desired heat exchange and the wall facing the outside of the machine being able to be thicker, forming an efficient insulation which counteracts a loss of heat to the outside.

The total capacity of the cavities (11, 12, 13) substantially corresponds to the quantity of water required for carrying out the most water-intensive treatment cycle.

Thus the water admitted into the tub remains in these cavities, which enable the water which they contain to be brought either to ambient temperature, generally higher than the temperature of the water from the water network, or a higher so-called pre-heating temperature by the recovery of a portion of the calories from the water from the preceding cycle, in particular the washing cycle. This particularity of the supply circuit of the tub enables a substantial reduction in the expenditure of heating energy, which is known to constitute the majority of the consumption of the appliance.

The diagram of FIG. 3 is a simplified diagram to illustrate the circulation of the water in the appliance according to the invention. The tub, referenced C in this figure, as described above, has hollow side walls which jointly form the buffer tank, referenced R.

Thus the tank R is supplied by the water from the water network by means of a pipe 15 downstream of a general solenoid valve 15a, the water passing via a flowmeter 16 and at the outlet thereof being able to be conducted into the tank R directly by the pipe 17 which is opened or closed by a solenoid valve 18 or indirectly by the pipe 19 which is opened or closed by a solenoid valve 20, via a water softener 21. A pipe 22 which is opened or closed by a solenoid valve 23 connects the tank to the interior of the tub C. A level sensor 24 is arranged inside one of the cavities forming the tank R, for example at mid-filling height. This sensor makes it possible to determine, as a function of a set value, the quantity of water which has to be admitted into the tank or delivered into the washing tub for optimal operation of the different phases of the appliance. It also enables the hardness of the water admitted into the tank to be determined and thus, by an appropriate treatment of this information by the controller, the degree of softening of this water to be adjusted, either during filling or for a specific number of washing operations.

Conventionally the tub C contains, as is most often but not necessarily the case, three spray arms 25, 26, 27 which are inserted into a recirculation circuit 28 comprising a pump 29 connected to a water heater, not shown. A thermostat 30 enables the temperature of the water to be detected. Moreover, the tub is connected to the sewer by a pipe 31 provided with a drain pump 32.

Finally, the man/machine interface panel 33 is shown on this diagram, which makes it possible to control and stop the operation of the machine and to determine the desired operating program. This panel is connected to a controller 34 which provides the control of the different operating phases.

It is understood, for example, that for an operating cycle with a pre-wash, the operation of the appliance is carried out in the following manner:

The user selects by means of the interface 33 a program with a pre-wash. This choice firstly involves the actuation of the drain pump 32 during a specific time period. Then the solenoid valve 23 is kept open during a specific time period. The controller 34 then opens the solenoid valve 18 at the inlet of the tank so that the level sensor 24 reaches a specific filling level. This detection makes it possible to calibrate the flowmeter 16. At the same time, the level sensor 24 measures the conductivity and thus the hardness of the water admitted, the value thereof being processed by the controller in order to define the degree of softening which has to be established as a function of this hardness of the water from the water network. The filling of the tank can continue, with the knowledge that the flowmeter has been calibrated for half filling. Thus the filling can be stopped in good time. The water admitted into the tub C is then recycled by the pump 29, which is connected to the water heater, during a programmed duration and at a temperature monitored by the thermostat 30. At the end of the pre-wash cycle, the drain pump 32 is actuated in order to drain the tub.

During this first cycle, a heat exchange has taken place between the interior of the tub C and the water which has been previously admitted into the tank R. Thus when the washing cycle starts, the water admitted into the tub, at a volume determined by the selected washing cycle, has been subjected to a pre-heating which makes it possible to save a part of the energy designed to bring it to the washing temperature determined by the program selected by the user.

At the start of the washing cycle, the water from the water network is admitted again into the tank R to supplement that used for the washing and, as above, it receives calories from the tub C during the washing and will be pre-heated for the following pre-rinsing phase. This water could originate at least partially from the water softener 21 according to the data from the level sensor 24 interpreted by the controller. Once the washing cycle has been carried out, the water is drained from the tub and the program continues with the pre-rinsing followed by rinsing according to the same sequences, namely a buffer storage of water in the tank R.

After rinsing, the water present in the tank is kept in reserve for future use of the appliance at a temperature which is in any case higher than that of the water delivered by the water network.

A systematic measurement of the conductivity of the water at regular intervals can be provided in the controller of the appliance, so as to adjust the softening thereof in an optimal manner since it is frequently the case that the water from the water network has a variable hardness.