EP0239025A2

EP0239025A2 - Laundry washing machine with washing liquid heating device

Info

Publication number: EP0239025A2
Application number: EP87104117A
Authority: EP
Inventors: Maurizio Mori; Olindo Regazzo
Original assignee: Industrie Zanussi SpA; Zanussi Elettrodomestici SpA
Current assignee: Industrie Zanussi SpA
Priority date: 1986-03-26
Filing date: 1987-03-20
Publication date: 1987-09-30
Also published as: EP0239025A3; IT8645715A0; IT1192072B

Abstract

A laundry washing machine, particularly of the type in which the laundry is sprinkled by recirculation of the washing liquid, provided with a washing liquid heating device (26) disposed exterior of the laundering tub (11).

The heating device (26) comprises an instant heat exchanger associated to the washing liquid recirculation conduit (23).

The proposed solution permits the liquid circulation system of the machine to be simplified, washing liquid filtering problems to be reduced, and the efficiency of the heating device to be improved.

Description

The present invention relates to a laundry washing machine particularly of the type in which the laundry is sprinkled by recirculation of the washing liquid, the machine being provided with a device for heating the washing liquid contained in the machine.
A laundry washing machine of this type is described for instance in European Patent Application No. 0146719 and comprises a washing liquid collecting receptacle disposed below the laundering tub, and a pump operable to take in the washing liquid collected in the receptacle for sprinkling the laundry contained in a rotatable drum mounted in the laundering tub. Disposed within the collecting receptacle is a heater element (usually an armoured electric resistor) for heating the washing liquid to the temperature required for the laundering operation.
As generally known, the laundry - particularly depending on the type of fabrics and degree of wear - tends to shed certain amounts of loose fiebrs during the washing operation, such fibers tending to collect in the washing liquid collecting receptacle. The receptacle is of rather reduced dimensions, and the presence therein of a fluid flow obstacle in the form of the heater element promotes a condition in which the loose fibers tend to be deposited on the heater element itself.
This problem may be aggravated in the case that the water supplied to the machine has a high degree of hardness, promoting the formation on the heater element of mineral incrustations favouring the deposit of loose fibers thereon.
An obvious solution to this problem is offered by the employ of a suitable fine-mesh filter for retaining loose fibers. This solution, however, complicates the construction of the washing liquid collecting receptacle and requires frequent intervention for cleaning the filter.
It would therefore be desirable, and is a main object of the invention, to provide a radical solution to this problem by concurrently simplifying the liquid circulation system of the machine so as to render the operation of the laundry washing machine more reliable and efficient.
The solution essentially consists in the elimination of the washing liquid collecting receptacle and the provision of means for heating the washing liquid directly in the recirculation conduit of the machine.
The invention is thus directed to a laundry washing machine substantially comprising a laundering tub, a rotatable drum mounted in the tub for containing the laundry, and a washing liquid recirculation system including a pump and conduit means connecting the bottom portion of the tub to the top portion thereof.
According to the invention, a laundry washing machine of this type is characterized in that an instant heat exchanger is associated to the recirculation conduit means, and at least one thermostat for controlling the temperature of the washing liquid is applied to the recirculation conduit means at a portion thereof between the heat exchanger and an inlet portion at the top portion of the laundering tub.
The objects and characteristics of the invention will become more clearly evident from the following description, given by way of example with reference to the accompanying drawings, wherein:

fig. 1 shows a diagrammatical sectional view of a laundry washing machine of the front-loading type, provided with a heating device according to a first embodiment of the invention,
figs. 2 and 3 show a sideview and a cross-sectional view, respectively, of the heating device employed in the embodiment of fig. 1, and
fig. 4 shows a diagrammatical sectional view of a laundry washing machine of the top-loading type provided with a heating device according to a second embodiment of the invention.

The front-loading laundry washing machine shown in fig. 1 substantially comprises a housing 10, a laundering tub 11 mounted in housign 10, and a rotatable drum 12 for containing the laundry mounted in tub 11 and adapted to be rotated by a motor 13 via a belt and pulley transmission.
Water is supplied to tub 11 through an inlet conduit 14 provided with a valve 15 and a detergent container 16, and connected to a top portion of tub 11 through a flexible hose 17.
Through another flexible hose 18 a bottom portion of tub 11 communicates with a chamber 19 containing a filter 20 for retaining foreign bodies which might otherwise damage the liquid circulation system of the machine.
Connected to chamber 19 of filter 20 are the intakes of a discharge pump 21 and a recirculation pump 22. A recirculation conduit 23 connects the outlet of the latter to an opening at the top of tub 11 for sprinkling the washing liquid recirculated by pump 22 onto the laundry contained in drum 12.
Pump 22 receives the washing liquid from flexible hose 18 through a connecting conduit 24, and is additionally connected to chamber 19 of filter 20 for recuperating any detergents precipitated in the chamber.
This arrangement results in a self-cleaning effect of filter 20, thus eliminating the necessity of frequent cleaning thereof.
Associated to recirculation conduit 23 is a washing liquid heating device 26 according to the invention.
In the embodiment shown more clearly in figs. 2 and 3, heating device 26 comprises a block 27 made of a material of high thermal conductivity, for example aluminum, having an electric resistor 28 inserted therein, and recirculation conduit 23 passing therethrough.
Heating device 26 is suitable enclosed in an insulating liner 29 for avoiding the dispersion of heat.
Heating device 26 substantially acts as an instant heat exchanger and is preferably disposed adjacent a location of entry of recirculation conduit 23 into tub 11, so as to ensure that the washing liquid impinges on the laundry at the temperature required for the washing operation, i.e. without heat losses by dispersion.
A thermostat 30 (fig. 1) for controlling this temperature is disposed on recirculation conduit 23 at a portion thereof between heat exchanger 26 and the end portion of the conduit entering laundering tub 11 at the top thereof.
The invention is also applicable to a laundry washing machine of the top-loading type as illustrated in fig. 4. In a machine of this type, the recirculation of the washing liquid is brought about by means of a pump 31 taking the washing liquid from a chamber 32 containing a filter 33 and communicating with the bottom portion of a laundering tub 34. The top portion of the latter is connected to a charging opening 35 by a sealing bellows 36.
Rotatably mounted in tub 34 is a drum 37 for containing the laundry to be washed.
The washing liquid is recirculated towards tub 34 through a recirculation conduit 38 connected at one end to the outlet of pump 31 and opening into the top portion of tub 34 through sealing bellows 36.
According to the invention, recirculation conduit 38 has a portion 39 of suitable length thereof formed as a closely wound helical coil.
Inserted into helical coil 39 is an electric resistor 40 in a manner to form an instant heat exchanger. Electric resistor 40 is forced into the passage formed by the windings of coil 39 to thus ensure a high heat exchange efficiency in both heat conduction and radiation.
Also in this case it is possible to eliminate the washing liquid collecting receptacle and to thereby avoid any problems doe to deposits of loose fibers and mineral incrustations.
As in the first embodiment, a thermostat 41 is mounted on recirculation conduit 38 between heat exchanger 39 and the entry of the conduit into bellows 36, for controlling the temperature of the washing liquid.
In both embodiments it is understood that the laundry washing machine is provided with suitable control and safety devices for the correct operation of the appliance.
The two embodiments described are both based on the principle of providing an instant heat exchanger associated to the recirculation conduit, to thereby simplify the liquid circulation system of the machine, reduce the number of obstacles to the flow of the washing liquid, and improve the efficiency of the heating device.
It is evident that the two embodiments of this device as described with reference to laundry washing machines of two different types are selectively applicable to laundry washing machines of practically any type and may to this purpose be modified or supplemented as required by the construction of any particular machine.

Claims

1. A laundry washing machine substantially comprising a laundering tub, a rotatable drum mounted in said tub for containing the laundry, and a washing liquid recirculation system including a pump and conduit means connecting the bottom portion of said tub to the top portion thereof, characterized in that an instant heat exchanger (26,39-40) is associated to said recirculation conduit means (23,38), and at least one thermostat (30,41) for controlling the temperature of the washing liquid is applied to said recirculation conduit means at a portion thereof between said heat exchanger (26, 39-40) and an inlet portion at the top portion of said laundering tub (11, 34).

2. A laundry washing machine according to claim 1, characterized in that said heat exchanger (26, 39-40) is located on said recirculation conduit means (23, 38) adjacent a portion thereof entering the top portion of said laundering tub (11, 34).

3. A laundry washing machine according to claim 1, characterized in that said heat exchanger (26) comprises a block (27) made of a material having high thermal conductivity, preferably aluminum, and having an electric resistor (28) inserted therein, said recirculation conduit means (23) passing through said thermally conductive block.

4. A laundry washing machine according to claim 1, characterized in that said heat exchanger comprises a portion (39) of said recirculation conduit means (38) formed as a closely wound helical coil surrounding an electric resistor (40).