Dishwasher tank

Abstract

The invention relates to a dishwasher tank comprising a bottom wall (2) secured to a lower frame (1), a top wall (6), two side walls (3, 4) and a back wall (5), wherein at least one of the walls is associated with a buffer holding tank for the water intended to be used for washing operations, characterised in that the side and back walls (2, 3, 4, 5) of the tank are made of a moulded plastics material, are hollow, are independent of one another and are sealingly assembled, and in that the cavities (11, 12, 13) in the hollow walls (3, 4, 5) communicate with each other via pipes which are provided in the frame (1) or the bottom wall (2) of the tank in order to jointly constitute the abovementioned holding tank.

Description

[0001] Dishwasher tub

[0002] BACKGROUND OF THE INVENTION

[0003] A dishwasher has a washing, rinsing, and drying tank made of either stainless steel or plastic. This washing tank is generally fixed to a lower frame that forms the support for all the power equipment necessary for the operation of the appliance (pumps, solenoid valves, filters, fluid channels, heating elements, etc.).

[0004] Generally, this tank is made in a single piece and is connected by through holes to the various distribution, evacuation and circulation pipes of the washing water leading to complicated assembly operations which can only be correctly carried out in the factory. All this determines the size of the device, therefore the volume occupied by the latter during the various phases of its transport and storage from its place of manufacture to the user's home.

[0005] Furthermore, with a view to achieving a certain sobriety in terms of energy consumption, knowing that the energy consumption of a dishwasher is mainly due (approximately 80%) to the heating of the washing water, means are being sought for recovering heat from the washing liquid before it is drained from the tank. There are, in the state of the art, documents which describe dishwashers in which a sort of buffer tank is attached to one of the side walls of the tank so that this wall constitutes a heat exchanger between the tank and this tank. This makes it possible to preheat the water contained in the tank, coming from the softener, for a subsequent washing or rinsing operation in the tank. This state of the art is illustrated by documents DE 80 19951 and DE 33 16716.

[0006] The object of the invention is a dishwasher tub structure which makes it possible, on the one hand, to save part of the energy spent on heating the water and, on the other hand, to simplify the various assembly operations so that they can be carried out on-site at the user's premises, in particular, in order to facilitate maintenance and repairs which are favorable to reducing the obsolescence of the appliance and even to be able to deliver the appliance in sub-assemblies, dismantled, to the user who can easily build it at home, with the advantage of a significant reduction in the volume of the appliance between its manufacture and its use.

[0007] SUBJECT OF THE INVENTION

[0008] For this purpose, the dishwasher tank according to the invention complies with claim 1.

[0009] This arrangement has the advantage of allowing the water to be preheated while waiting to be used, for the next dish or for a later phase of the wash cycle, while preserving the possibilities of easy installation on site, by a professional or even by a user.

[0010] One of the walls advantageously carries a level sensor for the water contained in the tank, arranged at a level which corresponds to a known fraction, for example half, of the total volume of the tank.

[0011] This sensor also acts as a water resistivity sensor, which it controls in order to adjust the degree of hardness of the water supplied by the network to the dishwasher. This function is ensured, in state-of-the-art appliances, by a uniform pre-setting for all of them in the factory. However, water hardness varies greatly from one distribution network to another and even within the same network depending on the source of the water supplying it.

[0012] In a particular embodiment, the walls of the tank are independent of each other, made of molded plastic material and are assembled to the adjacent walls by means of centering devices for their relative positioning and by lever clamps exerting pressure between two adjacent walls in the direction of their respective centering to strengthen their support on each other and compress a sealing joint at this support.

[0013] Other characteristics and advantages will emerge from the description given below of exemplary embodiments of the invention.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Reference will be made to the attached drawings, including:

[0016] [Fig 1] is a diagram illustrating the general structure of the dishwasher tub according to the invention,

[0017] [Fig 2] is a diagram of an alternative embodiment of the three side walls of the tank according to the invention,

[0018] [Fig 3] is a simplified diagram of the hydraulic circuit of the machine according to the invention.

[0019] DETAILED DESCRIPTION OF THE INVENTION

[0020] In Figure 1, the lower wall 2 of the tank, preferably made of plastic, is shown on a base 1 which, in a known manner, forms a support frame for the various power elements of the device (pumps, valves, heating elements, etc.). This bottom wall is secured to this frame by any suitable means, whether removable or not.

[0021] The side walls of the tank which frame the opening are marked 3 and 4. The bottom wall is marked 5 and the top wall is marked 6. Preferably, the five walls are independent and made of molded plastic.

[0022] At the base of the walls 3, 4 and 5, as well as under the edge 6a of the wall 6, centering devices such as 7 are provided which ensure correct positioning of the walls relative to each other by cooperating with housings 8 provided correspondingly in the edges of the walls 2, 3, 4 and 5. There are also centering devices not shown at the adjacent vertical edges of the walls 3, 4 and 5.

[0023] Lever clamps 9 allow, in the manner of a clamp, to hold the adjacent edges of the walls in tight support to crush a seal such as 10 which ensures, between the different walls, the sealing of the tank. Of course, the seals implemented in the invention are designed - which is not shown - to bypass the centering devices.

[0024] In Figure 2, the walls 3, 4 and 5 are shown schematically and in partial section to show the fact that they are hollow so as to constitute water cavities 11, 12, 13, intermediate or buffer between the water inlet and the supply of the tank. These cavities communicate with each other by means of pipes (not shown) arranged in the chassis and / or formed in, or carried under, the lower wall of the tank and connecting the end pieces 14 of each cavity in series or in parallel to these pipes to constitute a single tank. It will be noted that the molded plastic construction of each wall allows simplified manufacturing compared to a double metal wall or a tank attached to the external face of a steel tank wall.This design also allows the thickness of the tank walls to be adjusted; the one adjacent to the tank can be relatively thin to promote the desired heat exchange and the one facing the outside of the machine can be thicker, forming an effective insulator to prevent heat loss to the outside.

[0025] The total capacity of the cavities (11, 12, 13) corresponds approximately to the quantity of water required to carry out the most water-intensive treatment cycle.

[0026] Thus, the water admitted into the tank remains in these cavities which allow the water they contain to be brought either to ambient temperature, generally higher than the temperature of the network water, or to a higher temperature called preheating by recovering part of the calories from the water from the previous cycle, in particular the washing cycle. This particularity of the tank supply circuit allows a significant reduction in the expenditure of heating energy which is known to constitute the largest part of the appliance's consumption.

[0027] The diagram in Figure 3 is a simplified diagram to illustrate the circulation of water in the apparatus according to the invention. The tank, denoted C, in this figure, has, as previously described, hollow side walls forming, together, the buffer tank denoted R.

[0028] Thus, the tank R is supplied with water from the network by means of a pipe 15 downstream of a general solenoid valve 15a, which passes through a flow meter 16, at the outlet of which it can be directed into the tank R directly by the pipe 17 open or closed by a solenoid valve 18 or indirectly by the pipe 19 open or closed by a solenoid valve 20, via a water softener 21. A pipe 22 open or closed by a solenoid valve 23, connects the tank to the inside of the tank C. A level detector 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, according to a setpoint, the quantity of water that must be admitted into the tank or delivered into the washing tank for optimal operation of the different phases of the appliance.It also makes it possible to determine the hardness of the water admitted into the tank and therefore, by appropriate processing of this information by the controller, to adjust the degree of softening of this water, either during filling or for a given number of washing operations. Conventionally, the tank C contains, as is most often the case but not necessarily, three spray arms 25, 26, 27 which are inserted into a recirculation circuit 28 comprising a pump 29 associated with a water heater not shown. A thermostat 30 makes it possible to detect the temperature of the water. In addition, the tank is connected to the drain by a pipe 31 equipped with a drain pump 32.

[0029] Finally, this diagram shows the human-machine interface panel 33, which allows the operation of the machine to be controlled and stopped and the desired operating program to be determined. This panel is connected to a controller 34 which controls the various operating phases.

[0030] It is understood that, for example, for an operating cycle with pre-wash, the operation of the device is carried out as follows:

[0031] By means of the interface 33, the user selects a program with pre-wash. This selection first involves activating the drain pump 32 for a determined time. Then the solenoid valve 23 is kept open for a determined time. The controller 34 then opens the tank inlet solenoid valve 18 to reach a filling level determined by the level detector 24. This detection makes it possible to calibrate the flow meter 16. At the same time, the level detector 24 measures the conductivity and therefore the hardness of the admitted water, the value of which will be processed by the controller to define the degree of softening that will have to be established according to this hardness of the network water. The filling of the tank can continue, knowing that the flow meter has been calibrated for a half-fill. It can therefore be stopped in good time.The water admitted into tank C is then recycled by pump 29 associated with the water heater for a programmed duration and at a temperature monitored by thermostat 30. At the end of the pre-wash cycle, drain pump 32 is activated to drain the tank.

[0032] During this first cycle, a heat exchange takes place between the interior of the tank C and the water which has previously been admitted into the tank R. Thus, when the washing cycle begins, the water admitted into the tank, in a volume determined by the washing cycle chosen, has undergone preheating which makes it possible to save a part of the energy intended to bring it to the washing temperature determined by the program chosen by the user.

[0033] At the start of the wash cycle, the mains water is again admitted into the tank R in addition to that used for washing and, as before, it receives calories from the tank C during washing and will be preheated for the following pre-rinse phase. This water may be, at least in part, from the water softener 21 according to the data from the level detector 24 interpreted by the controller. Once the wash cycle is completed, the water is drained from the tank and the program continues with the pre-rinse followed by the rinse according to the same sequences, namely a buffer storage of the water in the tank R.

[0034] After rinsing, the water in the tank is stored for future use of the appliance at a temperature that is in any case higher than that of the water supplied by the network.

[0035] The device controller can provide for a systematic measurement of the water conductivity at regular intervals, so as to adjust its softening optimally, as network water often has variable hardness.

Claims

Claims 1. Dishwasher tank comprising a lower wall (2) secured to a lower frame (1), an upper wall (6), two side walls (3, 4) and a bottom wall (5), in which at least one of the walls is associated with a buffer tank for holding water intended for washing operations, characterized in that the side and bottom walls (2, 3, 4, 5) of the tank are made of molded plastic material, are hollow, are independent of each other and are assembled in a sealed manner and in that the cavities (11, 12, 13) of the hollow walls (3, 4, 5) communicate with each other by pipes which are arranged in the frame (1) or the bottom wall (2) of the tank to together constitute the aforementioned holding tank.

2. Tank according to claim 1, characterized in that one of the cavities is provided with a sensor (24) for the level of the water contained in the tank arranged at a level which corresponds to a known fraction of the total volume of the tank (R) • 3. Tank according to claim 2 characterized in that the sensor (24) also acts as a sensor for the resistivity of the water which it controls in order to be able to adjust the degree of hardness of the water which is delivered by the network to the dishwasher.

4. Tank according to any one of the preceding claims, characterized in that the walls (2, 3, 4, 5, 6) of the tank are assembled to the adjacent walls by means of centering devices (7, 8) for their relative positioning and by lever clamps (9) exerting pressure between two adjacent walls in the direction of their respective centering to strengthen their support on each other and compress a sealing joint (10) at this support.

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