GB2265699A

GB2265699A - Switchable recirculation in a laundry drier

Info

Publication number: GB2265699A
Application number: GB9306400A
Authority: GB
Inventors: Guenter Wentzlaff; Heinrich Boecker
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-04-02
Filing date: 1993-03-26
Publication date: 1993-10-06
Anticipated expiration: 2013-03-26
Also published as: GB2265699B; DE4211011C2; DE4211011A1; GB9306400D0

Abstract

A domestic laundry tumble dryer, of the kind having a rotatable tumbling drum 1, ducts which feed heated drying air to and discharge moisture-laden air from the drum and a heat-exchanger by which moisture from the discharged air can be precipitated by heat exchange with cooling ambient temperature air, has a changeover arrangement by which the moisture- lad en air and cooling air can follow alternative paths through the heat-exchanger and dryer, according to seasonal requirements. With crossover ducts 40, 41 in position ambient-temperature cooling air from intake 10 enters the heat- exchanger by inlet 7 and is subsequently discharged, while moisture-laden air from the drum 1 passes through link filter 16, enters the heat-exchanger by inlet 9 and is recirculated to the drum through a duct containing a heater. Replacement of crossover ducts 40, 41 by straight ducts 38, 39 causes cooling air from intake 10 to enter the heat-exchanger by inlet 9 and to leave it by the duct feeding the heater and drum. Alternatively changeover may be by flap valves in ducts between the intake 10, the drum 1 and the heat-exchanger inlets. <IMAGE>

Description

AIR ROUTING IN A LAUNDRY DRIER The present invention relates to a laundry

drier, especially a domestic laundry drier, and has particular reference to air routing in such a drier.

In DE-PS 30 27 900 there is disclosed a laundry drier in which an air-cooled plate condenser, which is installed in a housing constructed as a tunnel extending in the direction of flow of drying or process air, is used as heat exchanger. The process air to be cooled and to be dehumidified flows through the condenser in tunnel direction and in that case passes over large contact areas of hollow exchanger plates, the interior spaces of which are flowed through transversely to the process air by cooling air separated from the process air. Driers of that kind have proved themselves in operation, particularly since their air-cooled condensers, by comparison with previously used water-cooled condensers, mean that the drier concerned does not require a switchable water inflow.

The cooling air, which is warmed during the heat exchange, is delivered from the condenser into the installation region around the drier, whereby the air in this region gradually heats up. In the case of longer drying duration, this heating-up can contribute to a noticeable temperature rise in the air in the room. This might not be a disadvantage in the cool season when there is frequently artificial heating of living spaces. However, if laundry driers of that kind are operated at times in which the room air surrounding the drier is for natural reasons already warm enough for the occup ants, the additional heating due to exhausted cooling air that has been heated up can be a nuisance. Moreover, the further heating of the surrounding room air reduces the efficiency of the heat exchanger.

There is therefore a need for a laundry drier by which the operator can, in dependence on the temperature, which appears to be comfortable, of the ambient air, convert the drier operation causing heating of this air into an operation not increasing the air temperature any further.

According to the present invention there is provided a laundry drier c n rising a rotatable laundry drum, a feed duct to carry heated drying air to the drum, a discharge duct to carry moisture-laden drying air discharged from the drum, a heat exchanger to effect precipitation of moisture in the discharged drying air by way of heat exchange with cooling air, and means to enable such cooling air to enter the feed duct after flowing through the heat exchanger and the discharged drying air to depart from the drier after flowing through the heat exchanger.

In a preferred embodiment, the drier comprises a drum arranged to be rotatable in the course of a drying or process air duct, which contains a blower and heating means, and a heat exchanger by which moisture from the process air flowing away from the drum in circulating air operation can be precipitated by means of exchanger elements cooled by cooling air. Means are provided by which the cooling air, after flowing through the heat exchanger is introducible into the process air duct and the process air, after flowing through the heat exchanger, is dischargeable into the open, and devices are also provided for conducting the departing process air out of the place of installation of the drier. Means of that kind can be controllable manually by the operator or, for example, controllable by an electrical circuit which itself is controlled by a sensor according to the temperature of the air around the drier.

In one preferred refinement, the equipment comprises connecting means in the form of convertible channels, of which one set provided for circulating air operation of the drier contains a first channel insert for connection of the discharge air duct coming from the drum with a process air or first inlet of the heat exchanger and a second channel insert for connection of a cooling air intake or induction opening with a cooling air or second inlet of the heat exchanger, and of which another set provided for the air exhaust operation of the drier contains a first channel insert for connection of the discharge air duct coming from the drum with the cooling air inlet of the heat exchanger and a second channel insert for connection of the cooling air induction opening with the process air inlet of the heat exchanger. The set of which another set provided for the air exhaust operation of the drier contains a first channel insert for connection of the discharge air duct coming from the drum with the cooling air inlet of the heat exchanger and a second channel insert for connection of the cooling air induction opening with the process air inlet of the heat exchanger. The set for circulating air operation and the set for air exhaust operation can be inserted into the heat exchanger by the operator according to need. Depending on the set used, either the process air is dehumidified and kept in circulation and the cooling air after flowing through the heat exchanger is discharged into the open, or the process air after dehumidification in the heat exchanger is exhausted into the open and the cooling air after heating in the heat exchanger is introduced into the process air feed duct. Since the conversion of the sets is as a rule required only in the transition periods of a year, for example at the beginning and end of summer, no excessive imposition on the operator is represented by this measure.

According to a further advantageous embodiment, the equipment can comprise switchable channel parts which connect the discharge duct coming from the drum in a first switch setting with the process air inlet and in a second switch setting with the cooling air inlet of the heat exchanger, and which connect the respective other inlet of the heat exchanger with the cooling air induction opening.

In this embodiment, storage of an exchange set for the heat exchanger is not necessary. Rather, the drier itself contains switchable connecting means so that actual changeover of channel parts or of a heat exchanger insert is not required.

In a further embodiment, the switchable channel parts can have two ports, disposed alongside each other of the process air inlet and of the cooling air entry, the ports being arranged symmetrically with respect to an exit opening lying opposite them, of the discharge duct coming from the laundry drum. A centre setting flap, which is arranged symmetrically to the ports and has a pivot axis between them, can in a first switch setting produce a connection to the process air inlet and in the second switch setting 6 connection to the cooling air inlet. In addition, two setting flaps, which are mounted externally of the ports and movable together with the centre flap, can in the first switch setting connect the cooling air inlet and in the second switch setting the process air inlet with the cooling air induction opening. In this arrangement, a space-saving construction of the switchable channel parts and a simply designed actuator for the operator is possible.

Expediently, the switchable channel parts are connected with an electrically actuable control device, in which case the actuator can be merely a switch, for example in the operation panel. This might be the simplest arrangement for the operator.

For preference, the electrical actuation is dependent on a signal from a temperature sensor in the neighbourhood of the drier. In that case, the action by the operator can be restricted to a once only or an occasional setting of the temperature sensor. In some circumstances, a fixed setting of the temperature sensor may even be of advantage. Then, no action by the operator is required.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a diagram showing the routing of drying or process air is and cooling air in a domestic laundry drier embodying the invention; Fig. 2 is a perspective view of a heat exchanger, with a withdrawable exchanger element insert, for such a drier; Fig. 3 is a perspective view of a heat exchanger element insert for use in such a heat exchanger; Fig. 4 is a perspective view of another heat exchanger element insert for use in such a heat exchanger; Fig. 5 is a horizontal section through the insert of Fig. 4, at the level of a process air exhaust channel; Fig. 6 is a horizontal section through the insert of Fig. 4, at the level of a cooling air feed channel; Fig. 7 is a view showing the outer channel arrangement for a heat exchanger with an insert according to Figs. 4 to 6; Fig. 8 is a view showing the outer channel arrangement of another heat exchanger, which uses convertible or switchable channel parts; Fig. 9 is a view showing channel part sets for use between a process air exit of the drier drum and the outer channel arrangement, in conjunction with the heat exchanger of Fig. 8; Fig. 10 is a view showing another form of switchable channel parts in front of the inlets of a heat exchanger; and Fig. 11 is a view showing yet another form of switchable channel parts in front of the inlets of a heat exchanger.

Referring now to the drawings, there is shown in Fig. 1 a diagram of part of a drier which comprises a rotatable laundry drum 1 disposed in a process or drying air circulation path, for which purpose the drum has an air inlet 2 and an air outlet 3. A blower 4 and a heater 5, which respectively impel the air into the drum 1 and heat the air, are connected in front of the inlet 2.

In the position of duct setting equipment 6 illustrated in Fig.

1, the outlet 3 is connected by way of a discharge section of a duct 12 with a process air inlet 7 of a heat exchanger 8. A cooling air inlet 9 of the heat exchanger is in that case connected directly with a cooling air induction opening 10, which can be disposed at the outward side of the housing of the drier. An outlet 11 of the heat exchanger 8 is connected to a feed section of the duct 12, in the course of which are arranged the blower 4, the heater 5 and the drum 1. A cooling air outlet 13 of the heat exchanger 8 is connected by way of a blower 14 with a discharge opening 15, which like the cooling air induction opening 10 can be disposed at the housing outer side. 5 A lint filter 16, which is illustrated schematically in Figs. 9 and 10, should be arranged in the discharge section of the duct 12, in order to protect the equipment 6 and above all the heat exchanger 8 to a large extent against being clogged by fluff. The blower 14 can be arranged not in the illustrated position but between the induction opening 10 and the inlet 9, as illustrated irk dashed lines. Because of possible sealing problems within the heat exchanger 8 in connection with an exchanger element insert, an arrangement of the blower 14 at the outlet 13 may be more advantageous, since induction pressure within the heat exchanger 8 would belong to the induction of ambient air through the seal leakage places of the heat exchanger and to its joint use in the process air circuit. Thereagainst, compressed air in the heat exchanger 8 can lead to leakage losses of still usable process air. The equipment 6 can be actuated by hand or as illustrated here, by an electrical control device 55, a setting signal of which is triggered by a measurement signal of a temperature transmitter 56 for the air temperature from the vicinity of the laundry drier.

The heat exchanger 8 can comprise a housing 17 and an insert 18 (or 22), as shown in Fig. 2. The insert 18 comprises hollow heat exchange plates 19, the interior spaces of which are flowed through by the cooling air and the surfaces of which are brushed by the process air, similarly to the heat exchanger described in DE-OS 30 27 900. Handles 20 mounted at the front of the insert enable manual withdrawal of the insert 18 from the housing 17. The inflow of the process air to the inlet 7 of the insert takes place through a slot 21 in the top 5 of the housing 17.

Such an insert 18 can be constructed as shown in Fig. 3 without the front plate provided with handles 20 according to Fig. 2. The plate interior spaces conduct the cooling air from the cooling air inlet 9 to the cooling air outlet 13 opposite thereto and the spaces between the plate conduct the process air from the inlet 7 to the outlet 11.

Such an insert 22 can, however, be constructed according to Fig. 4, again illustrated without a front plate. In that case the plate interior spaces conduct the cooling air from the inlet 9 to the outlet 11, which as seen in direction of flow is disposed around the righthand corner, and the spaces between the plates conduct the process air from the inlet 7 to the outlet 13 disposed around the lefthand corner.

The insert 22 according to Fig. 4 is shown in Fig. 5 sectioned horizontally at the level of a process air exhaust channel, thus along an intermediate plate space. The shape of the intermediate plate space as a channel, which is bent around the corner post 23 illustrated at the bottom left, is easily recognisable. The very warm process air (arrow 24), which comes from the outlet 3 of the drum, enters at the inlet 7 into the intermediate spaces 25, delivers an appreciable part of the entrained quantity of heat to the plate surfaces and issues again as cooled exhaust air (arrow 26) at the cooling air outlet (13).

In correspondence with the shape of the exhaust air channels in the intermediate plate spaces 25, the cooling air feed channels in the hollow plate spaces 27 are bent around the post 28 illustrated in Fig. 6 at the top right. In that case, the cooling air (arrow 29) inducted by way of the opening 10 (Fig. 1) from the vicinity of the drier enters by way of the cooling air inlet 9 into the plate interior spaces 27, there takes up the heat, passed on by the process air (arrow 24, Fig. 5), from the plate surfaces and passes as preheated process air (arrow 30) at the outlet 11 into the feed section of the duct 12.

Fig. 7 shows this form of the heat exchanger together with the outer channel arrangement. This is on the one hand the cooling air duct with the blower 14 and on the other hand the feed section of the duct 12 with the blower 4. This arrangement corresponds to the usual mode of construction of air-cooled laundry driers, in which a heat exchanger element insert 18, in which the process air and the cooling air are according to Fig. 3 conducted in cross-flow, is arranged in the heat exchanger 8.

In the case of the use of the insert 22 according to Figs. 4 to 6, the two blowers 4 and 14 would then be connected directly in series. To compensate for this, the blowers 4 and 14 connected in series could be operated with a common total power which is sufficient to maintain the entire air circulation from the induction opening 10 by way of the heat exchanger 8, the duct 12 with the heater 5 and the drum 1 and the heat exchanger 8 to the cooling air outlet 13 in the desired manner. Alternatively, the power of one of the blowers, for example the blower 4, could be sufficient to maintain this circulation, in which case the blower 14 could be switched off.

The illustration of equipment by way of which the process air, after flowing through the heat exchanger, is dischargeable into the open and the cooling air, after flowing through the heat exchanger, is introducible into the feed section of the duct 12, can be effected without exchange of heat exchanger inserts, for example by way of the equipment according to Figs. 8 to 11 or equipment similar thereto. For this purpose, the heat exchanger 8 is provided with a single insert, by which the process air and the cooling air are conducted exclusively and transversely to each other in the heat exchanger 8.

The housing of the heat exchanger 8 contains stationary channel parts 31 and 32, which each have a respective connection opening 33 and 34, in front of the inlets 7 and 9.

These connection openings are directed upwardly and are in alignment on the one hand with the exit of the discharge section of the duct 12 coming from the laundry drum and on the other hand with the cooling air induction opening 10. A.third connection opening 35 of the stationary channel part 31 to the inlet 7 is in alignment with an oppositely disposed sealing surface 48 (Fig. 10), the purpose of which is explained further below.

The oppositely disposed connection openings as well as the sealing plate are disposed, like the connection openings 33 to 35, on a straight line and in one plane. Convertible or exchangeable channel parts serve for connection of respectively opposite connection openings or of neighbouring connection openings. In the embodiment of Fig. 9, the connection opening 35 can be dispensed with. The stationary channel part 31 is closed at this place, and one 11 - convertible channel part 36 has two equal length straight tube portions 38 and 39. which are each mechanically connected together, and which are set between the respective connection openings so as to directly connect the section of the duct 12 with the inlet 7 as well as the cooling air induction opening 10 with the inlet 9. The other channel part 37 can be exchanged against the channel part 37, as illustrated in Fig. 9. The part 37 has S-shaped curved tube portions and 41 which connect the cooling air induction opening 10 with the inlet 7 and the section of the duct 12 with the inlet 9. This channel part configuration corresponds to the diagram of Fig. 1, but in which the equipment 6 is connected with the cooling air induction opening 10. The circuit state actually illustrated in Fig. 1 results from use of the channel part 36.

An exchange of the channel parts 36 and 37 can be avoided by a three-membered channel part 42 according to Fig. 10, which is arranged to be laterally displaceable between the afore-mentioned connection openings 33 to 35 on the one hand an.d the opening 10 and discharge section of the duct 12 on the other hand. The channel part 42 consists of a straight tube portion 43, two tube portions 44 and 45 curved in S-shape in opposite sense and a sealing plate 46, which are all firmly connected mechanically together. The channel part 42 is mechanically displaceable, laterally out of the illustrated position, by a toothed rack drive 47 into a position towards the left, in which the straight tube portion 43 connects the opening 10 with the opening 34. In this position, the S-shaped tube portions come into a connection with the section of the duct 12 on the one hand and the connection opening 35 on the other hand, which as in the case of the opening 33 is connected with_the inlet 7 of the heat exchanger 8. Although the opening 33 is in this position also open to the connected Sshaped tube portion 45, this tube portion is closed at its upper opening by the closure plate 48. In the illustrated position, the additional connection opening 35 is closed by the sealing plate 46 of the channel part 42.

Since such convertible channel parts 36 and 37 or 42 might possibly take up too much space, switchable channel parts according to Fig. 11 are also possible as the channel-setting equipment 6. This equipment comprises a three-membered pivotal flap ground 49, which can be switched, manually or electrically, into the illustrated position or the position indicated by dashed lines. In the illustrated position, the opening 33 is connected with a lefthand channel branch 50 of the induction opening 10 by a flap 52, which is open for this connection. A flap 53 closes off a connection to the section of the duct 12. At the same time, however, this flap 53 is open for the connection of the opening 34 to the duct section, and a flap 54 closes off a connection of the opening 34 to a righthand channel branch 51 of the induction opening 10. The illustrated setting is thus provided for air exhaust operation and the position of the flaps indicated by dashed lines is for circulating air operation.

The illustrated embodiments are only examples of possibilities for varying the mode of operation of the drier. According to the actual construction of a laundry drier with a process air channel and a heat exchanger of the described kind, modifications departing from the illustrated embodiments may be necessary.

The laundry drier, in the air exhaust operation, thus in the converted setting or the switch setting of the channel parts or with exchange of the heat exchanger insert, is provided with devices for removal of exhaust air from the exit 13 out of the installation location of the drier, such as through windows or through a ventilation shaft. By comparison with exhaust air driers without a heat exchanger, a drier embodying the present invention has the advantage of the utilisation of waste heat.

Claims

- 14 CLAIMS

1 A laundry drier comprising a rotatable laundry drum, a feed duct to carry heated drying air to the drum, a discharge duct to carry moistureladen drying air discharged from the drum, a heat exchanger to effect precipitation of moisture in the discharged drying air by way of heat exchange with cooling air, and means to enable such cooling air to enter the feed duct after flowing through the heat exchanger and the discharged drying air to depart from the drier after flowing through the heat exchanger.

2. A drier as claimed in claim 1, comprising means to conduct such 10 departing air away from the drier.

3. A drier as claimed in claim 1 or claim 2, comprising a blower and heating means arranged in the feed duct.

4. A drier as claimed in any one of the preceding claims, wherein the heat exchanger has a first inlet and a second inlet and the drier further comprises air intake means for the cooling air.

5. - A drier as claimed in claim 4, the means to enable comprising alternatively effective first connecting means and second connecting means, the first connecting means being insertable to connect the discharge duct with the first inlet and the air intake means with the second inlet for a drying air circulation mode of operation of the drier and the second connecting means being insertable to connect the discharge duct with the second inlet and the air intake means with the first inlet for a drying air exhaust mode of operation of the drier.

6. A drier as claimed in claim 4, the means to enable comprising switchable connecting means arranged in a first switch setting to connect the discharge duct with the first inlet, in a second switch setting to connect the discharge duct with the second inlet and in each setting to connect the air intake means with the respective other inlet.

7. A drier as claimed in claim 4, comprising alternatively effective pluralities of heat exchange elements for the heat exchanger, one plurality being insertable to connect the discharge duct with the feed duct and the intake means with an exhaust outlet of the heat exchanger for a drying air circulation mode of operation of the drier and the other plurality being insertable to connect the discharge duct with the exhaust outlet and the intake means with the feed duct for a drying air exhaust mode of operation of the drier.

8. A drier as claimed in claim 6, the connecting means comprising two ports, which are disposed alongside each other and symmetrically with respect to an exit opening of the discharge duct and which are respectively connected to the first inlet and second inlet of the heat exchanger, a centre flap movable between a first setting in which one of the ports is connected to the discharge du ct exit opening and a second setting in which the other port is connected to the discharge duct exit opening and two outer flaps movable with the centre flap to connect said other port with the air intake means in the first setting and to connect said one port with the air intake means in the second setting.

9. A drier as claimed in claim 8, wherein the centre flap is pivotable about an axis between the ports and the outer flaps are pivotable about axes outside the ports.

10. A drier as claimed in any one of claims 6, 8 and 9, comprising electrically actuable drive means to effect switching of the connecting means.

11. A drier as claimed in claim 10, the drive means being actuable in response to a signal indicative of temperature in the region of the drier.

12. A laundry drier substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

13. A drier as claimed in claim 12 and substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

14. A drier as claimed in claim 12 and substantially as hereinbefore 15 described with reference to Fig. 3 of the accompanying drawings.

15. A drier as claimed in claim 12 and substantially as hereinbefore described with reference to Figs. 4 to 7 of the accompanying drawings.

16. A drier as claimed in claim 12 and substantially as hereinbefore described with reference to Figs. 8 and 9 of the accompanying drawings.

17. A drier as claimed in claim 12 and substantially as hereinbefore described with reference to Fig. 10 of the accompanying drawings.

18. A drier as claimed in claim 12 and substantially as hereinbefore described with reference to Fig. 11 of the accompanying drawings.