GB2286446A - Condenser tumble dryer with usage timer - Google Patents

Description

4 2286446 1 CONDENSER TUMBLE DRYER This invention relates to condenser

tumble dryers.

Tumble dryers usually employ a rotatable drum mounted in a cabinet, the cabinet having a door which can be opened to allow the load to be inserted into the drum. Heated air is circulated through the drum to dry the load. In a condenser dryer, the hot moist air leaving the drum is subjected to heat exchange with cooler, usually ambient atmospheric air, in a condenser, before the whole or part of the drier air is recirculated through the drum. The moisture condensing in the condenser can be drained or collected in a container which is periodically emptied.

In order to prevent fluff from blocking the condenser, a filter is provided through which passes the airstream leaving the drum. Usually such a fitter is mounted on the door of the cabinet, and the moist air passes through the filter before being channelled to the condenser. The filter must be periodically cleaned eg by washing it to remove lint from the filter mesh pores.

However, it is found that such a filter is not infallible, in the sense that small particles of dust or fluff can and do pass through the filter and then accumulate in the moist-air channels in the condenser. The condenser must therefore also be periodically cleaned, and is usually made to be removable for this reason.

2 While users are encouraged to clean the condenser regularly, this is not always done, and this results over a period of time in a noticeable deterioration in the performance of the dryer, sometimes to the extent that a service engineer is called out simply because the user does not appreciate the effect on the performance of the dryer that a partially blocked condenser can have.

The invention provides a condenser dryer which includes timer means arranged to operate an alarm in response to the dryer being operated for a predetermined length of time, and manual reset means for cancelling the alarm and for resetting the timer means.

The chances of the cleaning of the condenser being overlooked are now greatly reduced, since the user is provided with a warning at the appropriate times.

A condenser dryer constructed in accordance with the invention will now be described, byway of example, with reference to the accompanying drawings, in which:

Figure 1 is a front view of a condenser dryer; Figure 2 is a schematic view of the main programme timer of the dryer; Figure 3 is a schematic view of one of the cams of the timer of Figure 2; Figure 4 shows two of the windings of the drum motor; Figure 5 shows a timer for operating the condenser-cleaning alarm; Figure 6 shows the cams of the timer of Figure 5; and 3 Figure 7 shows a part of the circuit diagram of the alarm.

Referring to Figure 1, the condenser dryer, which is designed to match other kitchen appliances by virtue of having a plinth 1, comprises a drum 2 rotatably mounted in a cabinet 3 and accessible through a door 3a. The drying air recirculates through the drum: heated air enters an opening at the rear of the drum and leaves through the front of the drum, passing through a filter 4 (a part of which is shown) mounted in the door. The hot moist air is then channelled through tubes 5 of condenser 6, which run from front to rear of the dryer, while ambient air is blown from bottom to top of the condenser around the outside of the tubes. Moisture drains from the ends of the tubes, while the now almost dry air emerging from the rear of the condenser tubes is heated by electrical elements (not shown) and directed into the rear of the drum. An arrangement of this general type is described in British patent application number 2 214 623.

Most of the fluff carded in the recirculating airstream is trapped by the filter 4, and can be washed or brushed off when the door is opened. However, some passes through the filter and accumulates in the tubes 5 of the heat exchanger 6. The heat exchanger is for this reason removable from the dryer, and can be withdrawn axially from the front of the dryer i.e. perpendicular to the plane of the drawing. For this reason, cover plate 7 (shown partly cut away) can be removed to allow access to the condenser. When the condenser is removed, it can be run under a tap to allow water to run through the tubes 5 to wash away any deposited fibres. If such fibres are not 4 regularly cleaned away, the condenser becomes partially blocked over a period of time, making a significant difference to the effectiveness of the dryer.

Dryers have in the past carried labels advising of the need for regular cleaning of the condenser, but this has often not been done, the user being unaware of the impairment of the performance caused in this way.

In accordance with the invention, an alarm controlled by timer means operates after an interval commensurate with the period of operation of the dryer over which significant fluff build-up in the condenser can be expected. The alarm is cancelled by operating a rocker switch 8, but this is located behind the cover plate 7. The user must therefore remove the cover plate 7 in order to operate the rocker switch. The intention is that, once the cover plate 7 is removed, the user is more likely to use the opportunity to withdraw the condenser and clean it.

The length of operation of the dryer is set by means of an electromechanical programme timer 9, illustrated schematically in Figure 2. A particular period is set by the programme timer 9 at the outset, and contacts operated by the cams maintain the heater on for a set period and the drum motor on for a set period. The cams are driven by a motor 12 of the electromechanical timer. Contacts operated by the cam 10 are responsible for operating the drum motor (not shown) in known manner, first for a longer period e.g. four and a half minutes in one direction and then for a shorter period e.g. half a minute in the reverse direction. The contact 1 Oc is closed when the angled part of the follower 1 Oa reaches the notch 1 Ob, and contact 1 Od is closed for the remainder of each revolution.

Closure of the contact 10c directly energises winding 13 of the drive motor, which is a split phase induction motor, and indirectly energises winding 14 via a capacitor 15, resulting in the reverse rotation of the motor, whereas closure of contact 1 Od energises winding 14 directly and winding 13 via the capacitor, resulting in forward rotation of the motor.

Advantage is taken of the shorter length of time of the reverse periods to permit the use of a timer means in the form of a twelve hour electromechanical timer 16 which records the cumulative length of the reverse periods only.

This timer 16 has two cams 17, 18 driven by motor 16a controlling the operation of respective contacts 19, 20. The live connection for the timer 16 is taken from timer 12 and is only powered during the shorter periods of reverse rotation during any period of operation of the dryer. The cams have profiles such that contact 19 is closed and contact 20 is open over 1800 of rotation of the timer and contact 20 is closed and contact 19 is open over the remainder of each revolution. Thus, one or other of the contacts 19, 20 is always closed.

Referring to Figure 7, the alarm consists of a buzzer 21 in series with one of the contacts 19, 20 by virtue of the rocker switch 8.

6 When the timer advances sufficiently far for the contact 19 to close, the buzzer 21 sounds. The user now has to remove the panel 7 in order to gain access to the rocker switch 8. This is operated, putting the buzzer in series with the contact 20, which by now has opened. When the timer has advanced through a further 1800, the contact 19 opens and the contact 20 closes, again requiring the rocker switch to be operated.

The buzzer is set off, in the example given, every sixty hours of use of the dryer which corresponds to the recommended intervals before cleaning the condenser becomes necessary. The timer 16 is only powered for half a minute per five minutes of rotation of the drum, i.e. for six minutes per hour of cycling of the drum and, since the timer 16 is a twelve hour timer which therefore undergoes half a revolution in six hours, the half revolution periods of time correspond to sixty hours of cycling of the drum.

The buzzer warns the user that sufficient time has elapsed to require the condenser to be cleaned. An advantage of the warning is that cleaning can be done at regular intervals, whereas hitherto it was difficult for a user to assess when the next cleaning was desirable.

Of course, variations may be made without departing from the scope of the invention. Thus, the periods of forward and reverse rotation may be different from the example given, and the timer 16 could operate for a different period. Also, the rocker Z 7 switch 8 could be mounted elsewhere, for example, on the fascia, and the removable panel could be dispensed with in this case. Further, the timer means could use additional cams on the electromechanical programme timer 9 instead of using the separate electromechanical timer 16.

If desired, the timer 16 could be replaced by an electronic timer arranged to open the contact 20 and close the contact 19, and vice versa, after selected periods of time. The electronic timer need not count the short reverse periods only, it could count usage of the machine directly by counting hours of use, or could count every switch on of the timer. It would still be desirable to position the rocker switch 8 behind the removable panel 7, but this is not essential. Further, the contacts 19, 20 and the switch 8 could be replaced by electronic switches, provided that there remained some form of manual reset for enabling the timer to be reset.

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Claims (6)

1. A condenser dryer which includes timer means arranged to operate an alarm in response to the dryer being operated for a predetermined length of time, and manual reset means for cancelling the alarm and for resetting the timer means.

2. A condenser dryer as claimed in claim 1, in which the manual reset means is located behind a panel which is removable to provide access to the condenser for cleaning purposes.

3. A condenser dryer as claimed in claim 1 or claim 2, which includes an electromechanical timer for setting the period of operation of the dryer, the timer being arranged to control contacts so that the drum repeatedly cycles through a forward rotation for a first period and a reverse rotation for a shorter, second, period, and the timer means is arranged to record the cumulative length of the periods of reverse rotation of the drum by means of an electromechanical timer.

4. A condenser dryer as claimed in claim 3, in which the electromechanical timer by means of which the cumulative length of reverse rotation periods is recorded is arranged to control two sets of contacts which are alternately closed with the other open during successive periods of half revolution of respective cams, and the manual reset means is operable to switch the alarm from a contact which has just closed to the other contact which has just opened in order to cancel the alarm and reset the timer.

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5. A condenser dryer as claimed in claim 3 or claim 4, in which there is a first electromechanical timer for setting the period of operation of the dryer, and a second electromechanical timer operating as timer means.

6. A condenser dryer substantially as herein described with reference to the accompanying drawings.