GB2094963A - Tumbler dryer - Google Patents

Abstract

A tumbler dryer comprising a tumbler (1), a heater (17), ducts (2, 3) for intake and exhaust of air, a ventilator (4), and a filter (26), comprises in addition a modularly built air recirculation part (8). This part comprises a two-sided centrifugal ventilator (14a) mounted in the recirculation duct (14). The actuating motor (14b) of the centrifugal ventilator is mounted outside the duct (14) and the outlet dampers (10, 11) opening to the ambiency and the recirculation duct (8), respectively. The dryer furthermore comprises an extra dust filter (25) located within the duct immediately in front of the heater (17). The dampers (10, 11) are forcibly controlled by automatic control means (15, 16) co-operating with a program device (18) associated with the tumbler (1) and the heater (17). This control is such that the dampers (10, 11) together and preferably in any position form a substantially constant flow area. In this manner a particularly reliable dryer is obtained which reduces considerably the consumption of energy during a tumbler drying process. <IMAGE>

Description

SPECIFICATION A tumbler dryer, especially for use in laundries The invention relates to a tumbler dryer, especially for use in laundries.

Tumbler dryers are known, which comprise a tumbler, a heater, ducts for intake and exhaust of air, a ventilator, and a filter. Air for the chamber of the tumbler is introduced from the ambiency through a heating chamber, whereas air from the dryer is exhausted to the ambiency through a particular exhaust duct.

It has been tried to recirculate part of the used air, but it is difficult to remove the moisture from the air in an economical manner.

The present invention relates to a tumbler dryer, whereby good economy is obtained since great importance has been attached to maintenance of the greatest possible number of calories from the exhausted air, and a rather considerable part of the used air is therefore recirculated to the tumbler chamber upon treatment in the remaining parts of the dryer.

The tumbler dryer according to the invention comprises an air recirculation part with dampers mutually forcibly controlled by means of automatic control means, said dampers opening to the ambiency and the recirculation duct, respectively, and together preferably in any position forming a substantially constant flow area.

The main object of the invention is to provide a particularly variable and reliable system for considerably reducing the consumption of energy during a tumbler drying process.

According to the invention, the control means may cooperate with a program device associated with the tumbler and the heater. An adjustment of this program device renders it possible to actuate the dryer at a temperature optimally tolerated by the laundry.

Furthermore, the control means and the program device may be adapted to open completely the air exhaust damper during the periods in which the laundry within the tumbler is changed and the heater is inefficient.

The above state is according to the invention established at the termination of the drying period by initiating the cooling of the laundry prior to its removal from the tumbler.

According to the invention, a two-sided centrifugal ventilator may be situated behind and in connection with the dampers of the recirculation duct, said ventilator preferably comprising forwardly curved shovels and an actuating motor mounted outside the recirculating duct. This ventilator is especially suited for ensuring a uniform distribution of the temperature of the air across the flow area in the following part of the recirculation duct, i.e. also when cold replacement air is introduced therein.

An air pipe inlet may according to the invention be connected immediately to the inlet end of the ventilator, said air inlet pipe being inclined both relative to the main direction of the airflow and to the axis direction of the ventilator. Such a particular shape and direction provide an efficient mixing of the cold intake air with the recirculation air at the intake of said recirculation air into the two-sided centrifugal ventilator.

According to a particular embodiment of the tumbler dryer according to the invention, a detachable filter such as a two-layer filter screen may be coupled after the centrifugal ventilator, but before the heater, whereby one layer is a widemeshed supporting net preferably with 20 to 40 and especially with 30 meshes per centimeter, and whereby the second layer is a fine-meshed net with 60 to 100 and preferably with 80 meshes per centimeter.

The shaft of the two-sided centrifugal ventilator may according to the invention comprise one bearing situated in a rigid wall, whereas the second bearing is situated on a thin membranelike, resilient wall portion in the recirculation duct.

An embodiment of the tumbler dryer according to the invention is illustrated in the drawing, in which Fig. 1 is a side view of an embodiment of the tumbler according to the invention, Fig. 2 is a diagrammatic, top view of the location of a centrifugal ventilator in the recirculation duct as well as of the air inlet pipe (fresh air), Fig. 3 is a side view of the location of Fig. 2, whereby the ventilator is omitted, Fig. 4 is a diagrammatic view of an example of the construction of the control means, and Fig. 5 illustrates the location of the control means in connection with the dampers as well as the location of the hygrometers and the connection thereof to the control means.

The tumbler dryer illustrated in Fig. 1 comprises a tumbler 1 for storat,e in batches of the laundry, and a duct 2 for intake of air for the tumbler 1, and a duct 3 for exhaust of the air used, the latter air being sucked out through the duct 3 by means of a ventilator 4. An air recirculation part 8 is connected to the duct 2 and the ventilator 4. In this part 8 the air removed through the duct 3 is reused by being recirculated to the duct 2 instead of being exhausted. The recirculation part comprises an exhaust damper 10 opening to the ambiency and a damper 11 opening to a recirculation duct 14. These dampers are forcibly controlled by means of automatic control means 15, 16.

The dampers 10 and 11 form together and preferably in any position a substantially constant flow area. The total air resistance adjacent the distributor 13 of the recirculation part is thus almost constant.

The control means 15 and 16 may co-operate with a program device 18 associated with the heater 1 7 of the tumbler. This program device is by means of a time control capable of emitting electric signals to the electric, hydraulic or pneumatic member 21, 22, 23, 24, 25, 26, and 27 of the control means 1 5 and 1 6. When the regulating members are hydraulic or pneumatic, the member 21 may be a four-way valve activated by an electric signal from the program device 18.

The control means according to the invention may furthermore comprise hygrometers 1 2a and 1 2b mounted in the distribution chamber 13.

A tumbler drying process usually runs as follows: Upon location of the wet laundry within the tumbler 1, the ventilators 4 and 1 4a as well as the heater 17 are started up. Subsequently, the dampers 10 and 1 1 are adjusted by means of the control means in such a manner that a relatively small amount of the exhaust air is exhausted into the atmosphere and the remaining amount of air is recirculated. Upon a predetermined drying period, or when a predetermined drying degree of the laundry has been reached, the damper 10 is completely opened, whereas the damper 11 is closed and the ventilator 1 4a is stopped. While the damper 11 is closed, all the air entering the tumbler is fresh air, i.e. the air from the air intake damper (the air inlet pipe) 20. During the intake of fresh air, the dried laundry within the tumbler 1 is changed for another fresh portion of wet laundry.

During the intake of fresh air through the pipe 20, a cooling of the dried laundry within the tumbler 1 is carried out, whereby said laundry is not subjected to heat damages.

Behind and in connection with the damper 11 of the circulating duct, a two-sided centrifugal ventilator 1 4a is mounted, which preferably comprises forwardly curved shovels. This ventilator is driven by an actuating motor I 4b mounted outside the recirculation duct by means of an outer belt pull. The shaft 1 4c of the ventilator is mounted in bearings 1 4d and 1 4e on the outside of the duct wall.

The air inlet pipe 20 is mounted at the inlet end of the ventilator 1 4a in such a manner that it forms an acute angle with the main direction of the air flow, i.e. the horizontal direction in Fig. 2, as well as with the axis direction of the ventilator.

The flow conditions at the two intake ends of the centrifugal ventilator 14a are indicated by the arrows a and b. The flow conditions at the arrow a are such that a slight underpressure exists at said arrow, which implies that fresh air is sucked into the tumbler through the pipe 20.

A detachable filter 25 is coupled after the centrifugal ventilator 1 4a, but before the heater 1 7. This filter may for instance be a two-layer filter screen, whereby one layer is a wide-meshed supporting net with 20 to 40 and preferably 30 meshes/cm, and the other layer is a fine-meshed net with 60 to 100 and preferably 80 meshes/cm.

It is important that this filter is cleaned at regular intervals, which also applies to a second filter 26 within the duct 3, said filter also being a two-layer filter.

It is important that the ventilator shaft 1 4c is extendabie in its longitudinal direction. When the shaft bearing 1 4e is fixedly mounted on a rigid duct wall, the shaft bearing 1 4d is mounted on a thin membrane-like, resilient wall portion 28 within the duct.

The invention may be varied in many ways without thereby deviating from the scope thereof.

Thus the recirculation part may be formed by modules connectable and adaptable to various tumbler dryers and local conditions. The module comprising the centrifugal ventilator may optionally be provided with a cleaning shutter possibly formed by the entire bottom of said module.

The control means 15 and 16 may as indicated in Fig. 4 comprises pistons and piston rods driven by a fluid from the regulating members 21-27.

Claims (10)

1. A tumbler dryer, especially for use in laundries, and comprising a tumbler, a heater, ducts for intake and exhaust of air, a ventilator, and a filter, characterised in that it comprises an air recirculation part with exhaust dampers mutually forcibly controlled by means of automatic control means and opening to the ambiency and the recirculation duct, respectively, said dampers together forming a substantially constant flow area.

2. A tumbler dryer as claimed in claim 1 characterised in that said dampers in any position together form a substantially constant flow area.

3. A tumbler dryer as claimed in claim 1 or 2, characterised in that the control means cooperates with a program device associated with the tumbler and the heater.

4. A tumbler dryer as claimed in claim 1, 2 or 3 characterised in that the control means comprises a hygrometer mounted in the distribution chamber.

5. A tumbler dryer as claimed in one or more of the preceding claims 1 to 4 characterised in that the control means and the program device can open completely the air dampers in the periods, in which the laundry within the tumbler is changed and the heater is inefficient.

6. A tumbler dryer as claimed in one or more of the preceding claims 1 to 5, characterised in that the state mentioned in the preceding claim is established at the termination of the drying period by initiating the cooling of the laundry prior to removal of said laundry from the tumbler.

7. A tumbler dryer as claimed in one or more of the preceding claims 1 to 6, characterised in that a two-sided centrifugal ventilator is situated behind and connected to the damper of the recirculation duct, said ventilator preferably comprising forwardly curved shovels and an actuating motor mounted outside the recirculation duct, the shaft of the ventilator being mounted in bearings on the outside of the duct walls.

8. A tumbler dryer as claimed in one or more of the preceding claims 1 to 7 characterised in that an air inlet pipe inclined both relative to the main direction of the air flow and to the axis direction of the ventilator is connected immediately to said inlet end of the ventilator.

9. A tumbler dryer as claimed in one or more of the preceding claims 1 to 8, characterised in that a detachable filter such as a two-layer filter screen is coupled after the centrifugal ventilator, but before the heater, whereby one layer is a wide-meshed supporting net preferably with 20 to 40 and especially with 30 meshes per centimeter, and whereby the second layer is a fine-meshed net with 60 to 100 and preferably 80 meshes per centimeter.

10. A tumbler dryer as claimed in one or more of the preceding claims 1 to 9, characterised in that one of the bearings of the ventilator shaft is situated in a rigid wall, whereas the second bearing is situated on a thin membrane-like, resilient wall portion in the recirculation duct.

1 1. A tumbler dryer substantially as hereinbefore described with reference to the accompanying drawing.