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(11) | EP 2 147 999 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Home laundry drier |
| (57) A home laundry drier (1) comprising an outer box casing (2) and, inside the casing,
a laundry drying container (3) for housing the laundry to be dried, and a hot-air
generator (7) for circulating a stream of hot air inside said laundry drying container
(3); the hot-air generator (7) comprising an air recirculating conduit (8) connected
at both ends to said laundry drying container (3), ventilating means (9) able to produce
an airflow (f) which flows along the recirculating conduit (8) and through the laundry
drying container (3), and a first heat-pump assembly (10) which is able to rapidly
cool the airflow (f) coming out from the laundry drying container (3) for condensing
the surplus moisture in said airflow (f), and then to rapidly heat the airflow (f)
returning back into said laundry drying container (3); the hot-air generator (7) also
comprising at least a second heat-pump assembly (15) which is also able to rapidly
cool the airflow (f) coming out from the laundry drying container (3) for condensing
the surplus moisture in said airflow (f), and then to rapidly heat the airflow (f)
returning back into said laundry drying container (3).
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[0002] More specifically, the present invention relates to a rotary-drum home laundry drier, to which the following description refers purely by way of example.
[0003] As is known, rotary-drum laundry driers usually comprise a substantially parallelepiped-shaped outer box casing; a cylindrical bell-shaped drum for housing the laundry to be dried, and which is housed in axially rotating manner inside the casing to rotate about its horizontally oriented longitudinal axis, directly facing a laundry loading and unloading opening formed in the front face of the casing; a door hinged to the front face of the casing to rotate to and from a rest position closing the opening in the front face of the casing to seal the casing and the bell-shaped drum; and an electric motor assembly for rotating the drum about its longitudinal axis inside the casing.
[0004] Rotary-drum laundry driers of the above type also comprise a closed-circuit, hot-air generator designed to circulate inside the revolving drum a stream of hot air with a low moisture content, and which flows through the revolving drum and over the laundry inside the drum to rapidly dry the laundry.
[0005] In some recently marketed rotary-drum laundry driers, the closed-circuit, hot-air generator comprises an air recirculating conduit having its two ends connected to the revolving drum, on opposite sides of the latter; an electric centrifugal fan located along the recirculating conduit to produce, inside the latter, an airflow which flows through the revolving drum; and finally a heat-pump assembly having its two heat exchangers located one after the other, along the air recirculating conduit. The first air/refrigerant heat exchanger of the heat-pump assembly provides for rapidly cooling the airflow arriving from the revolving drum to condense the surplus moisture in the airflow; whereas the second air/refrigerant heat exchanger of the heat-pump assembly provides for rapidly heating the airflow arriving from the first heat exchanger and directed back to the revolving drum, so that the airflow re-entering into the revolving drum is heated rapidly to a temperature higher than or equal to that of the air flowing out of the revolving drum.
[0006] More specifically, the heat-pump assembly of the hot-air generator generally comprises:
- a refrigerant reciprocating compressor which subjects a refrigerant in the gaseous state to compression, so that refrigerant pressure and temperature are much higher at the outlet than at the inlet of the reciprocating compressor;
- a first air/refrigerant heat exchanger, commonly referred to as the condenser, through which the refrigerant coming out from the compressor and the airflow entering into the revolving tub flow simultaneously, and which is designed so that the refrigerant releases heat to the airflow entering into the revolving drum, while at the same time condensing in the liquid state;
- a second air/refrigerant heat exchanger, commonly referred to as the evaporator, through which the refrigerant flowing to the compressor and the airflow coming out from the revolving drum flow simultaneously, and which is designed so that the refrigerant absorbs heat from the airflow arriving from revolving drum to cause condensation of the surplus moisture in the airflow, while at the same time completely turning back into the gaseous state; and
- a refrigerant expansion device which subjects the refrigerant flowing from the condenser to the evaporator to a rapid expansion, so that pressure and temperature of the refrigerant entering in the evaporator are much lower than pressure and temperature of the refrigerant coming out from the condenser, thus turning the refrigerant back into the gaseous state and completing the closed thermodynamic cycle in opposition to the reciprocating compressor, which provides for rapidly compressing the refrigerant.
[0007] Obviously, evaporator and condenser of the heat-pump assembly are located along the air recirculating conduit, so as that the evaporator provides for rapidly cooling the airflow arriving from the revolving drum to condense the surplus moisture in the airflow, and the condenser provides for rapidly heating the airflow arriving from the evaporator and directed back to the revolving drum, so that the airflow entering into the drum is heated rapidly to a temperature higher than or equal to that of the same air flowing out of the drum.
[0008] Unluckily, despite the fact that this type of rotary-drum laundry drier is highly efficient, the limited flexibility of the heat-pump assembly has been the object of frequent criticism by the final users. In fact, due to the use of a single-speed fixed-capacity reciprocating compressor, this type of rotary-drum laundry drier is quite noisy and can perform a unique type of drying cycle which is suitable for traditional clothing, but which can fatally damaged supersensitive clothing. These kind of clothing, in fact, gets fatally damaged when dried using hot air having temperature higher than 50°C.
[0009] It is the aim of the present invention to provide a rotary-drum home laundry drier designed to eliminate the aforementioned drawbacks.
[0010] According to the present invention, there is provided a home laundry drier as claimed in Claim 1 and preferably, though not necessarily, in any one of the Claims depending directly or indirectly on Claim 1.
[0011] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which :
- Figure 1 shows a section view, with parts removed for clarity, of a rotary-drum home laundry drier in accordance with the teachings of the present invention; and
- Figure 2 shows a schematic view of a variation of the Figure 1 laundry drier.
[0012] With reference to Figure 1, number 1 indicates as a whole a home laundry drier comprising a preferably, though not necessarily, parallelepiped-shaped outer box casing 2; a preferably, though not necessarily, cylindrical bell-shaped revolving drum 3 for housing the laundry to be dried, and which is fixed in axially rotating manner inside casing 2, directly facing a laundry loading and unloading opening 2a formed in the front face of casing 2; and a door 4 hinged to the front face of casing 2 to rotate to and from a rest position closing opening 2a in the front face to seal revolving drum 3.
[0013] More specifically, in the example shown revolving drum 3 rests horizontally inside casing 2 on a number of horizontal supporting rollers 5 which are fitted to casing 2 to let revolving drum 3 freely rotate about its longitudinal axis L.
[0014] Casing 2, revolving drum 3, door 4 and supporting rollers 5 are commonly known parts in the industry, and therefore not described in detail.
[0015] With reference to Figure 1, laundry drier 1 also comprises an electric motor assembly 6 for rotating, on command, revolving drum 3 about its longitudinal axis L inside casing 2; and a closed-circuit, hot-air generator 7 housed inside casing 2 and designed to circulate through revolving drum 3 a stream of hot air having a low moisture level, and which flows over and rapidly dries the laundry inside drum 3.
[0016] More specifically, closed-circuit, hot-air generator 7 provides for gradually drawing air from revolving drum 3; extracting surplus moisture from the air drawn from revolving drum 3; heating the dehumidified air to a predetermined temperature, normally higher than the temperature of the air from revolving drum 3; and feeding the heated, dehumidified air back into revolving drum 3, where it flows over, to rapidly dry, the laundry inside the drum.
[0017] In other words, hot-air generator 7 provides for continually dehumidifying and heating the air circulating inside revolving drum 3 to rapidly dry the laundry inside the drum, and substantially comprises:
an air recirculating conduit 8, the two ends of which are connected to revolving drum 3 on opposite sides of the latter;
an electric centrifugal fan 9, or other type of air circulating pump, located along recirculating conduit 8 to produce, inside recirculating conduit 8, an airflow f which flows into revolving drum 3 and over the laundry inside drum 5; and
a heat-pump assembly 10 which is able to rapidly cool the airflow f coming out from revolving drum 3 for condensing the surplus moisture in the airflow f, and then to rapidly heat the airflow f returning back into revolving drum 3, so that the airflow entering into revolving drum 3 is heated rapidly to a temperature higher than or equal to that of the same air flowing out of the revolving drum.
[0018] More specifically, in the example shown the intake end of recirculating conduit 8 is integrated in door 4, and is faced to the front opening of revolving drum 3; the end wall 3a of revolving drum 3 is perforated, or at any rate permeable to air, to permit air entry into drum 3; and the exhaust end of recirculating conduit 8 is coupled in airtight manner directly to the end wall 3a of revolving drum 3.
[0019] As regards electric centrifugal fan 9, it is structured to produce an airflow f flowing, along recirculating conduit 8, from the intake end of recirculating conduit 8, i.e. door 4, to the exhaust end of recirculating conduit 8, i.e. the perforated end wall 3a of revolving drum 3.
[0020] With reference to Figure 1, heat-pump assembly 10 operates in the same way as a traditional heat-pump - which is capable of transferring heat from one fluid to another using an intermediate gaseous refrigerant subjected to a closed thermodynamic cycle, the thermodynamic principles of which are widely known and therefore not described in detail - and comprises:
an electrically powered refrigerant compressing device 11 which subjects a gaseous refrigerant to compression (e.g. adiabatic compression) so that refrigerant pressure and temperature are much higher at the outlet than at the inlet of compressing device 11;
a first air/refrigerant heat exchanger 12 which is located along recirculating conduit 8 - preferably, thought not necessarily, downstream of centrifugal fan 9 - and is designed so that the airflow f from revolving drum 3 and the refrigerant flowing to the inlet of compressing device 11 flow through it simultaneously, allowing the refrigerant having a temperature lower than that of the airflow f, to absorb heat from the airflow f thus causing condensation of the surplus moisture in the airflow f;
a second air/refrigerant heat exchanger 13 which is located along recirculating conduit 8, downstream of air/refrigerant heat exchanger 12, and is designed so that the airflow f directed to revolving drum 3 and the refrigerant from the outlet of compressing device 11 flow through it simultaneously, allowing the refrigerant having a temperature greater than that of the airflow f to release heat to the airflow f, thus rapidly heating the airflow f to a temperature higher than of the airflow f coming out of the air/refrigerant heat exchanger 12, and preferably, thought not necessarily, also higher or equal to the temperature of the airflow f coming out of revolving drum 3; and
a throttling valve or similar refrigerant expansion device 14 which subjects the refrigerant flowing from the second air/refrigerant heat exchanger 13 to the first air/refrigerant heat exchanger 12 to a rapid expansion, so that pressure and temperature of the refrigerant entering in air/refrigerant heat exchanger 12 are much lower than pressure and temperature of the refrigerant coming out from air/refrigerant heat exchanger 13, thus completing the closed thermodynamic cycle in opposition to the compressing device 11, which provides for rapidly compressing the refrigerant.
[0021] Heat-pump assembly 10 finally comprises a number of suitable connecting pipes which connect refrigerant compressing device 11, heat exchanger 12, heat exchanger 13 and refrigerant expansion device 14 one to the other, so as to form a closed circuit allowing the refrigerant coming out from the outlet of compressing device 11 to flow, in sequence, through heat exchanger 13, refrigerant expansion device 14 and heat exchanger 12, before returning to the inlet of compressing device 11.
[0022] Differently from known home laundry dries, hot-air generator 7 also comprises at least a second heat-pump assembly 15 which, in cooperation with or in place of heat-pump assembly 10, is able to rapidly cool the airflow f coming out from revolving drum 3 for condensing the surplus moisture in the airflow f, and then to rapidly heat the airflow f returning back into revolving drum 3, so that the airflow entering into revolving drum 3 is heated rapidly to a temperature higher than or equal to that of the same air flowing out of the revolving drum.
[0023] With reference to Figure 1, likewise heat-pump assembly 10, heat-pump assembly 15 comprises:
an electrically powered refrigerant compressing device 16 which subjects a gaseous refrigerant to compression (e.g. adiabatic compression) so that refrigerant pressure and temperature are much higher at the outlet than at the inlet of compressing device 11;
a first air/refrigerant heat exchanger 17 which is located along recirculating conduit 8, upstream of heat exchanger 12 - and preferably, thought not necessarily, downstream of centrifugal fan 9 -, and is designed so that the airflow f from revolving drum 3 and the refrigerant flowing to the inlet of compressing device 16 flow through it simultaneously, allowing the refrigerant having a temperature lower than that of the airflow f, to absorb heat from the airflow f thus causing condensation of the surplus moisture in the airflow f;
a second air/refrigerant heat exchanger 18 which is located along recirculating conduit 8, downstream of air/refrigerant heat exchanger 17 and immediately upstream of heat exchanger 13, and is designed so that the airflow f directed to revolving drum 3 and the refrigerant from the outlet of compressing device 16 flow through it simultaneously, allowing the refrigerant having a temperature greater than that of the airflow f to release heat to the airflow f, thus rapidly heating the airflow f to a temperature higher than of the airflow f coming out of the air/refrigerant heat exchanger 12 and 17, and preferably, thought not necessarily, also higher or equal to the temperature of the airflow f coming out of revolving drum 3; and
a throttling valve or similar refrigerant expansion device 19 which subjects the refrigerant flowing from the second air/refrigerant heat exchanger 18 to the first air/refrigerant heat exchanger 17 to a rapid expansion, so that pressure and temperature of the refrigerant entering in air/refrigerant heat exchanger 17 are much lower than pressure and temperature of the refrigerant coming out from air/refrigerant heat exchanger 18, thus completing the closed thermodynamic cycle in opposition to the compressing device 16, which provides for rapidly compressing the refrigerant.
[0024] Likewise heat-pump assembly 10, also heat-pump assembly 15 comprises a number of suitable connecting pipes which connect refrigerant compressing device 16, heat exchanger 17, heat exchanger 18 and refrigerant expansion device 19 one to the other, so as to form a closed circuit allowing the refrigerant coming out from the outlet of compressing device 16 to flow, in sequence, through heat exchanger 18, refrigerant expansion device 19 and heat exchanger 17, before returning to the inlet of compressing device 16.
[0025] In addition to the above, capacity of refrigerant compressing device 11 may be equal to, or greater than, or lower than that of refrigerant compressing device 16, so that heating and cooling capabilities of heat-pump assembly 10 may be equal to, greater than, or lower than that of heat-pump assembly 15.
[0026] In particular, in the example shown, capacity of refrigerant compressing device 11 is equal to twice the capacity of refrigerant compressing device 16, so that the heating and cooling capabilities of heat-pump assembly 10 are approximately twice the heating and cooling capabilities of heat-pump assembly 15.
[0027] In addition to the above, refrigerant compressing device 11 is preferably, though not necessarily, a rotary compressor such as, for example, a rotary screw compressor, a rotary vane compressor or a scroll compressor. Similarly, in the example shown refrigerant compressing device 16 is preferably, though not necessarily, a rotary compressor too.
[0028] With reference to Figure 1, laundry drier 1 finally comprises an electronic central control unit 20 which can switch on and off compressing device 11 and compressing device 16 independently of each other, according to the particular drying cycle selected by the user, so as to activate heat-pump assemblies 10 and 15 either alternatively one to the other, or simultaneously.
[0029] General operation of home laundry drier 1 is clearly inferable from the above description, with no further explanation required.
[0030] The presence of two independent heat-pump assemblies has lots of advantages. By switching on only the small rotary compressor (compressing device 16), or only the big rotary compressor (compressing device 11), or both the small and the big rotary compressors, hot-air generator 7 offers three different power levels which significantly improves versatility of the laundry drier.
[0031] In fact, by switching on compressing devices 11 and 16 independently one to the other, laundry drier 1 can adapt the drying performances of hot-air generator 7 to the clothing inside revolving drum 3.
[0032] For example, heat-pump assembly 15 may be dimensioned for producing an airflow f of dehumidified warm air having, on entry into drum 3, temperature slightly lower than that admitted by the supersensitive clothing (namely 50°C); whereas heat-pump assembly 10 may be dimensioned for producing, in cooperation with heat-pump assembly 15, an airflow f of dehumidified warm air having, on entry into drum 3, temperature suitable for normal clothing (namely 70°C)
[0033] Moreover, during execution of a traditional drying cycle, control unit 20 can switch from heat-pump assembly 10 to heat-pump assembly 15 and vice versa, according to the real moisture level of the clothing inside revolving drum 3, thus optimizing electric power consumption.
[0034] In addition to the above, since production costs of refrigerant compressors increase in a more than proportional ration with respect to the capacity of compressor, the overall cost of refrigerant compressing devices 11 and 16 is significantly lower than the cost of a traditional refrigerant compressing device having a capacity equal to the sum of the capacities of compressing devices 11 and 16.
[0035] Finally, for the same performance, rotary compressors are smaller than reciprocating compressors, thus improving clearance into casing 2.
[0036] Clearly, changes may be made to home laundry drier 1 as described herein without, however, departing from the scope of the present invention.
[0037] For example, heat exchanger 18 of heat-pump assembly 15 may be located along recirculating conduit 8, downstream of heat exchanger 13; whereas heat exchanger 17 may be located along recirculating conduit 8, upstream of heat exchanger 12.
[0038] With reference to Figure 2, in a further variation of hot-air generator 7, heat exchanger 18 of heat-pump assembly 15 may be located along recirculating conduit 8, downstream of heat exchanger 13; and heat exchanger 17 may be located along recirculating conduit 8, between heat exchangers 12 and 13.
[0039] In which case, heat exchanger 17 of heat-pump assembly 15 may, optionally, be at least partially incorporated into heat exchanger 13 of heat-pump assembly 10, and the resulting air/refrigerant/refrigerant heat exchanger may be designed for allowing the refrigerant of heat-pump assembly 10 to release heat also to the refrigerant of heat-pump assembly 15 (i.e. not only to the airflow f directed to revolving drum 3), thus significantly improving the exergetic efficiency of the heat transfer process.
[0040] In fact, in this embodiment heat-pump assembly 10 may operate with a higher value of the refrigerant pressure along the high pressure side of the closed thermodynamic cycle, and heat-pump assembly 15 may operate with a higher value of the refrigerant pressure along the low pressure side of the closed thermodynamic cycle; thus drastically reducing energy consumption of refrigerant compressing devices 11 and 16.
[0041] This improvement of the exergetic efficiency leads to an unexpected outstanding improvement of the overall energy efficiency of the laundry drier, drastically reducing energy consumption.
[0042] Moreover, as is known the closed thermodynamic cycle performed by a heat-pump assembly is intrinsically unbalanced towards heat production: i.e. the heat released to the outside in the high-temperature heat exchanger in always greater than the heat absorbed from the outside in the low-temperature heat exchanger. In hot-air generators of laundry driers this unbalance makes extremely difficult to control the temperature of the airflow returning back into the revolving drum of the laundry drier. In today's laundry driers, this problem is solved providing the hot-air generator with an additional electrically operated external ventilating fan which cools the head of the refrigerant reciprocating compressor to dissipate the heat in excess produced by the heat-pump assembly.
[0043] In Figure 2 variation, heat-pump assembly 15 may be used for absorbing also the heat in excess produced by heat-pump assembly 10. In which case, a sole additional electrically operated external ventilating fan (non shown) may be used to dissipate the heat in excess produced by both heat-pump assemblies 10 and 15, thus reducing overall energy consumption of home laundry drier 1.
- an air recirculating conduit (8) connected at both ends to said laundry drying container (3);
- ventilating means (9) able to produce, along the recirculating conduit (8), an airflow (f) which flows through the laundry drying container (3); and
- a first heat-pump assembly (10) which is able to rapidly cool the airflow (f) coming out from the laundry drying container (3) for condensing the surplus moisture in said airflow (f), and then to rapidly heat the airflow (f) returning back into said laundry drying container (3);
said home laundry drier (1) being characterized in that said hot-air generator (7) also comprises at least a second heat-pump assembly (15) which is also able to rapidly cool the airflow (f) coming out from the laundry drying container (3) for condensing the surplus moisture in said airflow (f), and then to rapidly heat the airflow (f) returning back into said laundry drying container (3).