GB2250678A

GB2250678A - Dishwasher with water temperature sensor

Info

Publication number: GB2250678A
Application number: GB9126402A
Authority: GB
Inventors: Claudio Milocco; Alessandro Cantu; Elvio Tonus
Original assignee: Zanussi Elettrodomestici SpA
Current assignee: Electrolux Zanussi Elettrodomestici SpA
Priority date: 1990-12-13
Filing date: 1991-12-12
Publication date: 1992-06-17
Anticipated expiration: 2011-12-12
Also published as: DE9115014U1; IT9034093V0; ES1019551U; CA2057611A1; IT9034093U1; ES1019551Y; FR2670379B3; GB2250678B; GB9126402D0; IT223518Z2; FR2670379A1

Abstract

A dishwasher with a sensor for detecting the temperature of the water in a washing tank (1). The sensor (15) is outside the tank (1) and can exchange heat with the water through a wall of the tank. The sensor (15) is preferably fitted in a cavity (17) in a shaped portion (16) of a water sump (2) which forms the bottom of the tank, the cavity (17) communicating only with the exterior. <IMAGE>

Description

The present invention relates to an automatic dishwasher with at least one temperature sensor for detecting the temperature of the operating fluid in the machine.

As is known, dishwashers have means for controlling and operating their various operative members; in particular, these means are adapted to heat the water admitted to the washing tank and to detect its temperature, for example, in order to stop heating it when it reaches a predetermined temperature.

In modern dishwashers, the control and operating means normally include electronic devices and the water temperature is detected by at least one temperature sensor housed in the washing tank of the machine, for example, in the sump, in a position in which it is substantially immersed in the water under control. The temperature sensor is of the type which is hermetically encapsulated in order to ensure the necessary electrical insulation and is thus quite expensive; moreover, the mass constituting the capsule may cause undesired delays in the response of the sensor which, in ertain conditions may therefore be inaccurate.

Moreover, since the electrical connections for connecting the temperature sensor to the associated control and operating means of the machine have to be outside the washing tank, the tank must be perforated so that the sensor can be housed within it, and the hole must be hermetically sealed. The fitting of the temperature sensor is therefore quite complex, since it requires specific operations and the use of means for forming a hydraulic seal.

The object of the invention is to provide a dishwasher which has a simple and reliable water-temperature sensor which can be mounted in its operative position in a similarly simple and quick manner.

According to the invention, this object is achieved by a dishwasher with a water-temperature sensor incorporating the characteristics of the appended claims.

The characteristics and advantages of the invention will be come clearer from the following description which is given purely by way of non-limiting example.

The description refers to the one appended drawing, which is a partial section of a preferred embodiment of the dishwasher according to the invention.

With reference to the drawing, essentially, the dishwasher has a washing tank 1, the bottom of which includes a water sump, preferably made of plastics material.

In conventional manner, the sump 2 communicates with the rest of the washing tank 1 through a filter having a substantially frustoconical portion 4 and a substantially cylindrical central portion 5.

In the bottom of the sump 2 is a motor-driven pumping unit which may, for example, be formed substantially as described in US-A-4 799 855. In particular, the pumping unit includes a centrifugal circulation pump ó and a discharge pump 7 with a peripheral outlet. The impellers of the pumps 6, 7 are keyed to the drive shaft 8 of a reversible electric motor 9 so that one or other is driven, according to whether the shaft 3 rotates in a first direction or a second.The discharge pump 7 is adapted, in known manner, to send the water drawn from the bottom of the sump 2 to an outlet (not shown) and the circulation pump 6 has an axial intake section 10, positioned in the bottom of the sump 2, through which it takes in water in order to send it to its output 11 during the stages when the machine is washing. More precisely, the output 11 of the circulation pump is adapted to supply at least one rotating arm (not shown, for simplicity) which is disposed above the filter 3 for spraying the dishes to be washed. The dishwasher also includes at least one heating resistance 12 or the like for heating the water (possibly with the addition of detergent) which collects in the sump 2. The resistance 12 is preferably fitted in the bottom of the tank 1 above the filter 3.

The main operating members of the machine, such as the motor 9 and the heating resistance 12, may be considered to be operated, in known manner, by a programmer (not shown), preferably of the electronic type and including, for example, a Motorola 6804 or 6305 microprocessor. In particular, the drawing shows schematically a control and operating device 13 which is associated with the programmer and is adapted to supply a voltage to the heating resistance 12 from a supply 14, in a programmed manner, under the control of at least one temperature sensor 15. The control and operating device 13 is adapted, for example, to supply the resistance 12 during heating stages determined by the programmer until the water collected in the sump 2 reaches a predetermined temperature which is detected by the temperature sensor 15.As already stated, the programmer and the control and operating device 13 may be of any known type and in any case do not form part of the present invention.

According to one aspect of the invention, the sensor 15 is disposed outside the washing tank 1 and can exchange heat with the water in the tank through a wall of the tank.

More precisely, the sump 2 has a shaped, inwardly-projecting portion 16 which is preferably integral with the sump and has a cavity 17 which communicates only with the region outside the sump.

The sensor 15 is fitted in the cavity 17, in which it is preferably incorporated in a mass of thermally conductive paste or the like which, for simplicity, is not shown.

The sensor 15 may be fixed mechanically by a hollow support frame 21 through which the electrical terminals 18 of the sensor extend. Preferably, the frame 21 is partially force-fitted in the cavity 17 in the shaped portion 1u and has a bracket 19 which is fixed by means of a screw 20 to a blind, threaded hole 22 in the external surface of the sump 2.

In any case, the positioning of the sensor 15 outside the sump 2 ensures that it is completely insulated hydraulically (and electrically in the preferred embodiment, in which the sump 2 is made of plastics) from the water whose temperature it is to detect. To advantage, the temperature sensor 15 does not therefore need to be encapsulated but may be a non-specific, elementary sensor which is therefore reliable and cheap, such as, for example, a Siemens RTY 6 temperature sensor.

It will be clear to an expert in the art that the shaped portion 16 and the threaded hole 22 can easily be formed during the conventional moulding of the entire sump 2 and enables the temperature sensor 15 to be fitted securely and quickly without the need to use hydraulic sealing means.

Naturally, the functional accuracy of the sensor 15 depends upon its having a good heat-exchange relationship with the water whose temperature it is to detect, through the walls of the shaped portion 16.

For this reason, the shaped portion 16 preferably has thin walls (for example, with a maximum thickness of 1.5 mm) so as not to involve a substantial delay in the response of the temperature sensor 15. Moreover, the shaped portion 16 is preferably formed in the bottom of the sump 2 in a region adjacent the intake 10 of the circulation pump 6, that is, in a region in which there is always an adequate water-flow during the heating stages.

Naturally, the diswasher described may be modified in many ways without departing from the scope of the invention as defined in the appended claims.

Claims

1. A dishwasher with at least one sensor for detecting the temperature of the water in a washing tank, characterised in that the sensor (15) is disposed outside the tank (1) and can exchange heat with the water through a wall of the tank.

2. A diswasher according to Claim 1, in which the bottom of the washing tank includes a water sump, characterised in that the sump (2) has a shaped portion (16) which projects inwardly of the sump and has a cavity (17) which communicates only with the exterior of the sump and in which the temperature sensor (15) is fitted.

3. A dishwasher according to claim 1, including at least one pump for drawing the water from the bottom of the sump, characterised in that the shaped portion (16) is formed in the bottom of the sump (2) in a region adjacent the intake section (10) of the pump (6).

3. A dishwasher according to Claim 2, characterised in that the temperature sensor (15) is substantially immersed in a mass of thermally-conductive material within the cavity (17).

4. A dishwasher according to Claim 2, including at least one pump for drawing the water from the bottom of the sump, characterised in that the shaped portion (16; is formed in the bottom of the sump (2) in a region adjacent the intake section (10) of the pump (6).

5. A dishwasher according to Claim 2, characterised in that the temperature sensor (15) is mounted on a support frame (21) fixed removably to the outside of the sump (2).

Amendments to the claims have been filed as follows

1. A dishwasher with at least one sensor for detecting the temperature of the water collected in a bottom sump of a washing tank, characterised in that said sensor is disposed outside the tank and in he at- exchange relationship with the water through a wall of the sump, wherein the sump has a shaped portion which projects inwardly of the sump with a cavity which communicates only with the exterior of the sump and in which the temperature sensor is fitted.

2. A diswasher according to claim 1, characterised in that the temperature sensor (15) is substantially immersed in a mass of thermally-conductive material within the cavity (17).