EP0324649B1

EP0324649B1 - Tumble driers

Info

Publication number: EP0324649B1
Application number: EP89300332A
Authority: EP
Inventors: Keith Rollason; Derek John Watts; John Garfield Davies
Original assignee: Creda Ltd
Current assignee: Creda Ltd
Priority date: 1988-01-13
Filing date: 1989-01-13
Publication date: 1992-09-09
Also published as: DE68902744T2; EP0324649A1; DE68902744D1; GB2214279B; GB2214279A; GB8800726D0

Description

This invention relates to tumble driers.
It is known to provide heat exchangers to enable moisture to be removed from the air flow through the drum, a fan re-circulating air through a path which includes the drum and the heat exchanger. It is also known for such heat exchangers to be removable from the front of the drier, because the air flow through them picks up fibres from the load in the drum and from any filters provided, and such heat exchangers therefore tend to become clogged. Removal enables such heat exchangers to be cleaned. In some arrangements, one motor is provided to drive the drum and another is provided to drive the fan. In another arrangement (US-A-3032887), one motor drives both the drum and the fan for recirculating air. A second fan is provided for blowing air through the heat exchanger comprising tubes arranged at the front and running from side to side of the drier, the fan being driven by a pulley and belt. The size of the cabinet of the tumble drier is dictated by certain standard dimensions, and the packaging of the various items often causes problems.
According to the invention, the heat exchanger tubes are arranged substantially at right angles to the front of the drier, and the second fan is also arranged on a shaft of the motor, the motor shafts being parallel to the tubes and spaced therefrom in a direction from side to side of the drier.
The use of the drum motor for shaft-driving both fans and the arrangement of the motor and fans side-by-side with the heat exchanger tubes arranged substantially at right angles to the front of the drier produces a particularly compact arrangement with a relatively small opening in the front of the drier for withdrawal of the heat exchanger for cleaning purposes, as well as eliminating the need for a belt and pulley to drive the second fan.
A tumble drier constructed in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which:-

Figure 1 is a schematic perspective view of the tumble drier;
Figure 2 is a top plan view of the tumble drier, but with components down to and including the drum not shown;
Figure 3 is a side view of the tumble drier with a duct omitted for clarity;
Figure 4 is a front view of the tumble drier;
Figure 5 is an enlarged view of a fan and housing for re-circulating air flow; and
Figure 6 is a schematic perspective view of the condensate container.

The tumble drier comprises a rotatable drum 1 housed in a cabinet 2, the drum being mounted on a bearing 3 at the front of the machine and a bearing (not shown) at the rear of the machine. A load is inserted into the tub through a door 4. The drum 1 is rotated by a motor 5 by a drive belt 6. The load is dried by means of an air flow heated by a heating element (not shown) in duct 7, which air flow circulates through the drum and through a condenser in the form of a heat exchanger indicated generally by the reference numeral 8 in a closed loop (see arrows 9 to 12). The heat exchanger is cooled by a flow of atmospheric air (arrows 13, 14). Condensed moisture is collected in container 15.
The layout of the motor and fans for producing the air flows will now be described. The motor 5 has output shafts at each end. As well as driving the drum belt 6, the forward shaft 16 drives a fan 17 in a housing 18 in order to impel air through the drum. The rear shaft 19 drives a fan 20 in a housing 21 in order to impel atmospheric cooling air through the heat exchanger. The co-axially arranged motor and fans lie laterally with respect to the heat exchanger 8.
Referring to figure 5, the fan 17 consists of a rotatable fan wheel i.e. a wheel bearing curved blades 22 which is rotatable in a volute housing i.e. the outer periphery of the housing is in the shape of a scroll so that the clearance between the fan and the housing gradually increases towards the outlet 23, which is tangential to the fan wheel. The inlet is axially into the centre of the fan wheel. Such a fan has a high efficiency, i.e. a high air throughput, when the fan is rotated in the direction of the arrow, but a low throughput when the fan is rotated in the opposite direction. The fan 20 and its housing are identical to the fan 17 and its housing.
The heat exchanger 8 consists of a number of flat tubes 24 (through which the re-circulating air passes) which run longitudinally along the heat exchanger. At the front and rear ends the tubes are set into plastics panels 25, 26, which block the spaces between the tubes, and top and bottom panel 27, 28 have offset slots in then (the top one being shown at 38) for feeding the cooling air across the condenser tubes.
The heat exchanger 38 is housed in a chamber 30, with which the housing 18 communicates for the inlet to the heat exchanger (arrow 9). The re-circulating air flow is driven by the fan 17 through the tubes 24 and leaves the rear end 31 of the chamber (arrow 10), and enters the duct 7 which contains the heating element. The now heated re-circulating air enters the rear of the drum through a slot 32 and, after flowing through the drum, passes along a tapering duct 33 (arrow 12) and enters the fan housing 17 axially through an aperture 34. The heated and moist air is driven into the chamber 30 again. The front panel 35 of the chamber 30 can be opened (and a similar panel on the front of the cabinet 2 may be opened) in order to enable the heat exchanger 8 to be withdrawn longitudinally from the cabinet 14. Particles of fibre and of lint filters (not shown) will be entrained in the re-circulating air flow, and the heat exchanger should be periodically removed and cleaned to prevent it becoming clogged.
The cooling of the heat exchanger is effected by the fan 20. Cooling ambient air (arrow 13) from the atmosphere is drawn axially through inlet 35a into aperture 36 in the fan housing 21 and enters chamber 30 through slot 37 in the underside of the chamber. The air passes over the heat exchanger tubes 24 and leaves the chamber through slot 38 (arrow 14), which is offset relative to the slot 37 in order to cause turbulence in the cooling air flow and therefore promote better heat transfer. The air which has now been heated re-enters the atmosphere.
The side-by-side arrangement of the heat exchanger 8 on the one hand and the motor 5 and co-axial fans 17 and 20 on the other hand permits: the use of a single motor for the drum and two fans; an axial air entry into both fan housings; and accessibility of the heat exchanger from the front of the machine.
An electronic circuit is provided for periodically reversing the direction of rotation of the motor. Instead of providing equal periods of forward and reverse rotation as hitherto, the motor rotates the drums and fan in a repetitive cycle consisting of a forward rotation of five minutes and a reverse rotation of half a minute. In this way, the fans are operating in an efficient manner for around 90% of the time and in an inefficient manner only for around 10% of the time. Overall the air flow through the drum is effective for drying even though the air flow is subject to the impedance created by the condenser and the ducting of the re-circulating loop. Equally, the short reversal is effective for preventing tangling of the clothes, in the same way as equal length reversals were hitherto.
The use of unequal forward and reverse times permits the use of high efficiency fans but without the need for individual drive motors.
Referring to figure 3, the moisture from the re-circulating air leaving the drum condenses and runs from drains 39, 40 to the pump 40a (figure 1) which is powered by its own electric motor, and which pumps the liquid to a container 15. Referring to figure 6, the container is withdrawn by the user periodically to empty it and has means to prevent it being over filled.
Thus, container 15, when fully inserted, rests on spring-loaded pressure pad 42. An operating lever 43 pivoted at 44 passes through a slot 45 in support panel 46. One end rests on the upper surface of the container 15. The other end rests on a further lever 47 which, when depressed, operates a switch 48 which switches on the pump motor and the main motor as well.
When the container 41 becomes filled to a predetermined level, the weight is such that the pressure pad 42 is depressed by a predetermined amount. In turn, the end of the lever resting on the container is depressed and the other end raised, so that the switch 48 operates. The user then withdraws the container and empties it, and the switch remains in the off position. Only when the empty container has been re-inserted will the levers set the switch to the position in which the machine can re-start.
Various modifications may of course be made to the embodiment described without departing from the scope of the invention. Thus, although the motor 5 is a two pole capacitor start and run induction motor, instead it could be a relay start motor, or indeed a four pole motor could be used. Equally, different forward and reverse periods in the reversing cycle of the motor are possible: thus, the ratio of forward to reverse for each cylinder could be from 5:1 to 20:1, and the cycle time could be between three minutes and ten minutes. Also, the points of entry to and exit from the heat exchanger could be changed. If desired the heat exchanges could be water cooled instead of air cooled.

Claims

A tumble drier which comprises a rotatable drum (1), a first fan (17) for producing an air flow through the drum, a heat exchanger (8) comprising a plurality of tubes (24) through which air flow through the drum passes in use before being re-circulated to the drum and which is removable through an opening in the front of the drier, the first fan being arranged on a shaft (16) of a motor (5) for rotating the drum, a second fan (20) being provided for passing cooling air from the atmosphere through the heat exchanger (8), the second fan also being driven by the motor (5), characterised in that the heat exchanger tubes are arranged substantially at right angles to the front of the drier, and in that the second fan is also arranged on a shaft of the motor, the motor shafts being parallel to the tubes and spaced therefrom in a direction from side to side of the drier.
A tumble drier as claimed in claim 1, in which the motor (5) is arranged between the two fans (17, 20).
A tumble drier as claimed in claim 1 or claim 2, in which an inlet (37) for the cooling air is spaced along the length of the tubes relative to, and beneath, an outlet (38) for the cooling air, so that the cooling air passes along the length of the tubes as well as upwardly past the heat exchanger tubes.