GB2362997A

GB2362997A - Safety switch

Info

Publication number: GB2362997A
Application number: GB0012009A
Authority: GB
Inventors: Gwyn Morris
Original assignee: Hoover Ltd
Current assignee: Hoover Ltd
Priority date: 2000-05-19
Filing date: 2000-05-19
Publication date: 2001-12-05
Anticipated expiration: 2020-05-19
Also published as: GB0012009D0; GB2362997B

Abstract

A safety switch 17 for use in a tumble drier has an ON/OFF actuator 21 and a control member 19, which is movable between first and second positions according to the position of the tumble drier door. The control member 19 and actuator 21 co-operate to only permit the electrical condition of the switch 17 to change from OFF to ON when the actuator 21 is in its ON position and the control member 21 is its second (door closed) position. The electrical condition of the switch 17 changes from ON to OFF either when the actuator 21 is moved from its ON to its OFF position or when the control member 19 is moved from its second (door closed) position to its first position (door open)position. Thus, when the door 12 of the drier is open, the drier cannot be started. The drier can only be started once the door 12 is closed and the actuator 21 is moved from its OFF to its ON position. If the door 12 of the drier is opened during operation, the drier stops.

Description

2362997 Safety Switch This invention relates to a safety switch and more

particularly but not solely to a safety switch for a domestic warm-air laundry drier or so- called tumble drier.

Hitherto, tumble driers have required only one operating action to set the drier in operation, once the appliance has been connected to a power source and a drying programme has been selected. This operating action is usually closing of the loading door of the drier, whereby an on/off switch is actuated through some suitable linkage. The potential for accidental starting of such driers is thus considerable and, considering the propensity of small children and domestic animals to climb into the drier, most undesirable.

Regulations now require that heated domestic tumbledriers having a drum capacity of 100 litres or more should be equipped with a switching arrangement whereby, following connection to a power source and selection of a drying programme, two discrete operating actions are required to start the drier. These actions are first closing of the loading door, and second pressing a start button. 20 It will be appreciated that a single action is permitted by the regulations for stopping these large-capacity driers, since unintentional stopping of the drier does not have any safety implications. This action is either pressing the start button for a second time, or opening the door. Tumble driers of the above-mentioned type are known in which a relay circuit is employed to achieve the requirement of two operating actions. Closing of the drier door actuates a switch, whereupon power is supplied to the drier circuit. The operator then presses a momentary- action push-button switch, to start the drier, which has the effect of energising the relay coil. The relay contacts close, causing the relay to latch on in known manner, whereupon power is supplied to the drier control circuit, heater and drum drive motor, and the drier starts. Opening of the drier door breaks the circuit, 2 causing the drier to stop and the relay to unlatch. A disadvantage of this arrangement is that it is complicated and expensive.

We have now devised a safety switch, which alleviates the above-mentioned problems.

In accordance with this invention, as seen from a first aspect there is provided a safety switch having an OFF condition and an ON condition, an actuator moveable between OFF and ON positions, and a control member movable between first and second positions, wherein the control member and actuator co-operate to only permit the switch condition to change from OFF to ON when said actuator is in said ON position and said control member is in said second position, and wherein the switch condition is changed from ON to OFF either when said actuator is moved from said ON to said OFF position or when the control member is moved from said second position to said first position.

In a tumble drier, the actuator forms a START/STOP button on the front of the drier and the control member is connected to the loading door of the drier.

When the door of the drier is open, the drier cannot be started, since the control member is in the first position, wherein it does not co- operate with the actuator to allow the switch to change to said ON condition in which the drier would start.

When the door of the drier is closed, the control member moves to its second position and thereby can co-operate with the actuator, once the actuator is actuated to start the drier. If the door of the drier is opened during operation, the control member moves from the second to the first position and thus the switch condition is changed from ON to OFF, thereby stopping the drier.

It will be appreciated that the requirements of the legislation on tumble driers are met, since the door has to be closed and the actuator moved to the ON position before the 3 drier will start. Thus, it is not possible for children to climb into the drier and inadvertently start it by closing the door.

Furthermore, if the door is opened whist the drier is operating, the control member moves to said first position and thus the switch condition is changed from ON to OFF.

Preferably, the actuator is biassed into said OFF position, the control member being arranged to co-operate with the actuator when the latter is in said ON position and said control member is in said second position, to hold the actuator in said ON position. In this manner the actuator returns to its OFF position when the control member moves from said second to said first position as the door is opened. The actuator is returned to the OFF position and the drier will not restart when the door is closed again.

Another advantage of the present invention is that it is not possible for children to climb into the drier and then start it by reaching up to press the actuator, since the switch condition cannot change from OFF to ON when the door is open and the control member is in said second position.

Preferably, the actuator is locked in said OFF position when said control member is in said first position.

Alternatively or additionally, the actuator is preferably unable to change the switch condition from OFF to ON when said control member is in said first position.

The safety switch is less complicated and expensive to include in a tumble drier than conventional switch and relay circuits, since the requirement of two operating actions is implemented mechanically and thus a relay and the associated latching circuit is not required.

Conveniently, the drier is arranged to stop either when the actuator is moved from the ON to the OFF position or when the door is opened.

Preferably, the latching means are provided such that the actuator moves from the ON to the OFF position on 4 successive actuations when the control member is in said second position.

Preferably, the safety switch comprises a micro-switch incorporating a pair of electrical contacts, the state of connection between which changes between said OFF condition and said ON condition, and a switch member which is actuable to change the state of electrical connection, wherein the control member carries a projection which is displaced by the actuator in said ON position to actuate the switch member when said control member is in said second position.

Also, in accordance with this invention, as seen from second aspect there is provided a tumble drier incorporating safety switch having an OFF condition and an ON condition, an actuator moveable between OFF and ON positions, and a control member movable between first and second positions, wherein the control member and actuator co-operate to only permit the switch condition to change from OFF to ON when said actuator is in said ON position and said control member is in said second position, and wherein the switch condition is changed from ON to OFF either when said actuator is moved from said ON to said OFF position or when the control member is moved from said second position to said first position.

Preferably the actuator extends through a front panel of the drier and forms a START/STOP button for the drier.

Preferably, the position of the control member is controlled by the position of a loading door of the drier, the control member being in said first position when the door is open and vice-versa.

Preferably the control member is actuated by a projection on the door which engages the control member when the door is closed.

Preferably, a catch retains the loading door of the drier in its closed position, the catch being arranged to release the door when a predetermined force is applied to the door in the door opening direction.

An embodiment of this invention will now be described by way of examples only and with reference to the accompanying drawings, in which:

Figure 1 is a schematic front view of a tumble drier in 5 accordance with this invention; Figure 2 is a sectional view of a safety switch of the tumble drier Figure 1, with some parts being shown cut away; Figure 3 is a simplified sectional view along the line III-III of Figure 2; Figure 4 is a side view of the actuator of the safety switch of the tumble drier of Figure 1; Figure 5 is an enlarged view of a portion of the switch actuator of Figure 3, showing the operation of the latching mechanism; and is Figure 6 is a sectional view of an alternative embodiment of safety switch, with some parts being shown cut away.

Referring to Figure 1 of the drawings, there is shown a tumble drier 10 comprising a cabinet 11 having a circular loading door 12, which is retained in its closed position by a conventional detent latch 13. The detent latch 13 retains the door 12 in the closed position. a simple outward force applied to the side of the door 12 remote from its hinge 14 is sufficient to overcome the holding force of the detent latch 13 and open the door 12: This force may be applied from outside or inside the machine and thus it is possible for children to open the machine if they become trapped inside the drier 10.

Contained within the tumble drier cabinet 11 is a door interlock mechanism comprising a bell crank 15 pivoted to the front panel of the cabinet 11, a push rod 16, pivotally connected at its lower end to the end of a horizontal arm of the bell-crank 15, and a safety switch 17, connected to the opposite end of the push rod 16. The bell-crank 15 is mounted, so that a rectangular aperture 18, formed in the lower end of 6 its vertical arm is engaged by a rearwardly projecting finger (not shown) on the door 12, when the door 12 is closed. The f inger is bent at its mid-point, such that on entering the aperture 16 it abuts the side wall thereof, thereby rotating the bell crank 15 in a clockwise direction about its pivot point and urging the push rod 16 upwardly. Correspondingly, when the door 12 is opened, the bell crank 15 rotates in a counter-clockwise direction under a spring bias and the push rod 16 moves downwardly.

Referring to Figures 2 and 3 of the drawings, the upper end of the push rod 16 is connected to the lower end of a control member 19 of the safety switch 17. The control member 19 is constrained to slide vertically in a body 20 of the safety switch 17, which is mounted to the front panel of the drier by means of lugs 23. An elongate actuator 21 is constrained to slide horizontally in the body 20 of the safety switch 17, in a direction perpendicular to the front panel. An outer end of the actuator 21 projects from the front panel, so that the actuator 21 can be actuated to start or stop the drier. The inner end of the actuator 21 is juxtaposed with the actuating button of a micro-switch 22. A spring 24 biases the actuator 21 in the outward direction and a spring 25 biases the control member 19 in the downwards direction, which in turn biases the bell crank 15 in a counter-clockwise direction via the push rod 16 linkage.

The control member 19 is generally c-shaped in section, as shown in Figure 3 and the actuator 21 and control member 19 are configured to slide in mutually perpendicular directions against each other. As described previously, when the door 12 is opened, the bell crank 15 rotates in a counter- clockwise direction under the bias of the spring 25 and the push rod 16 and the control member 19 move downwardly. In this position, a slot 26 in the upper end of the control member 19 receives a projection 27 formed on the upper surface of the actuator 21, thereby preventing any sliding motion of the actuator 21.

7 The actuator 21 comprises a latching mechanism, which retains the actuator 12 in an ON position when it is pushed inwardly and which returns the actuator 12 to and OFF position when it is pushed inwardly again.

Referring to Figures 4 and 5 of the drawings, the latching mechanism comprises an irregular- shaped recess 28 formed in a side wall of the actuator 21. A disc 29 having outwardly projecting pins formed centrally on its opposite sides is mounted in face-to-face contact with the side wall of the actuator 21, such that a pin on one side thereof extends into the irregular-shaped recess 28. The pin on the opposite side of the disc 29 extends into a vertical slot 31, which is formed in a side wall of the body 20 of the safety switch 17. The disc 29 extends through a large aperture 30 in an upright is portion of the control member 19, disposed between the opposed side walls of the actuator 21 and the body 20 of the safety switch 17. It will be appreciated that the disc 29 is free to move solely in the vertical direction.

As already stated, the actuator 21 is biassed outwardly by the spring 24. In the OFF position, the actuator 21 is retained inside the body 20 of the safety switch 17 by the pin, which extends from the disc 29 into the aperture 28 in the side wall of the actuator 21 and abuts against the innermost wall thereof, as shown at 29a in Figure 5. When the actuator 21 is pressed inwardly (in direction A), the pin rides vertically upwardly and over an inclined surface of a projecting cam 32 disposed inside the aperture 28 in the side wall of the actuator 21, until it reaches a position behind the cam 32 at the innermost position of the actuator 21, as shown at 29b in Figure 5.

When pressure on the actuator 21 is released, it moves outwardly under the bias of the spring 24, until the pin comes to rest against the outwardlyfacing surface of the cam 32, as shown at 29c, thereby preventing further outwards movement of the actuator 21 and holding the latter in the ON position. When 8 the actuator 21 is pressed for a second time, an inclined surface 33 of the recess 28 shifts the pin downwards and out of engagement with the cam 32, thereby permitting the actuator 21 to return under the bias of the spring 24 to its OFF 5 position.

It will be appreciated that in the ON position, the inner end of the actuator.21 actuates the micro-switch 22 and the drier starts. To stop the drier, the actuator 21 is pressed a second time, whereby the latching mechanism is released and the actuator 21 is biassed away from the micro-switch 22 and into the OFF position by the force of the spring 24.

Referring again to Figures 2 and 3 of the drawings, as shown, the actuator 21 is in its OFF (outermost) position and the control member 19 is in its raised (door closed) position, is wherein the projection 27 on the upper surface of the actuator 21 is out of engagement with the slot 26 on the upper end of the control member 19 and the actuator 21 is thus free to slide within the body 20 of the safety switch 17. If the door 12 is opened when the actuator 21 is in its OFF position, the bell- crank 15 is free to rotate in the counter-clockwise direction under the spring bias and the control member 19 moves downwardly, as herein before described: This causes the projection 27 formed on the upper surface of the actuator 21 to enter the slot 26 in the upper end of the control member 19, thereby preventing the actuator 21 from being depressed inwardly to turn the tumble drier on. Thus, it is not possible to start the tumble drier when the door 12 is opened.

If the door 12 is opened whilst the drier is operating, the control member 19 again moves downwardly, as herein before described. This action causes the upper end of the large aperture 30 in the upright portion of the control member 19 to abut the disc 29, which extends through the aperture, thereby moving the disc 29 vertically downwardly and out of the position shown at 29c in Figure 5. As the disc 29 moves downwardly, it disengages the cam 32 and permitting the 9 actuator 21 to return under the bias of the spring 24 to its OFF position, whereupon the drier stops and the actuator 21 is again locked in the OFF position until the door is closed again.

It will be appreciated that the door 12 has to be closed and the actuator 21 depressed before the drier will start. Thus, it is not possible for children to climb into the drier and inadvertently start it by closing the door. It is also not possible for children to climb into the drier and then start it by reaching up to press the actuator 21, since the actuator 21 is always locked in the OFF position when the door 12 is open.

Conveniently, the drier is arranged to stop either when the actuator 21 is pressed to move it from the ON to the OFF position or when the door is opened. In the latter case, the actuator 21 is automatically returned to its OFF position.

In the unlikely event that the drier is started with someone inside the machine, it is possible for that person to push open door from inside, thereby stopping the machine.

A disadvantage of the above-mentioned safety switch is that the drier will continue to operate if the actuator 21 is held in whilst the door is opened.

Referring to Figure 6 of the drawings, in order to overcome this problem in an alternative embodiment of safety switch 17, the inner end of the actuator 21 is shortened, so that the latter cannot directly engage the actuating button of the micro-switch 22 when pressed in.

The control member 19 carries an extension strip 34 of spring steel having an outer end which is positioned between the inner end of the actuator 21 and the actuating button of the micro- switch 22 when the control member 19 moves to the door closed position. Accordingly, when the actuator 21 is pressed in, its inner end engages the free end of the extension strip 34 and presses it against the actuating button of the micro-switch 22 to operate the drier in the above-mentioned switch manner.

However, if the actuator 21 is held in whilst the door is opened the drier will stop, since the extension strip 34 moves away from between the actuating button of the micro- 22 and the inner end of the actuator 21, as the control member 19 moves to the door open position.

The slot 26 in the upper end of the control member 19 and the projection 27 may be omitted, since it does not matter if the actuator 21 is pressed in whilst the door is open, since the actuator 21 is not sufficiently long to reach the actuating button of the micro-switch 22 unless the control member 19 is in the door closed position.

It will be appreciated that the switch of Figure 6 operates in exactly the same manner as the embodiment of Figure 2 but additionally safeguards against the drier continuing to operate if the actuator 21 is held in whilst the door is opened.

11

Claims

Claims

1. A safety switch having an OFF condition and an ON condition, an actuator moveable between OFF and ON positions, and a control member movable between first and second positions, wherein the control member and actuator co-operate to only permit the switch condition to change from OFF to ON when said actuator is in said ON position and said control member is in said second position, and wherein the switch condition is changed from ON to OFF either when said actuator is moved from said ON to said OFF position or when the control member is moved from said second position to said first position.

2. A safety switch as claimed in claim 1, in which the actuator is biassed into said OFF position, the control member being arranged to co- operate with the actuator when the latter is in said ON position and said control member is in said second position, to hold the actuator in said ON position.

A safety switch as claimed in claims 1 or 2, in which the actuator is locked in said OFF position when said control member is in said first position.

4. A safety switch as claimed in any preceding claim, in which the actuator is unable to change the switch condition from OFF to ON when said control member is in said first position.

S. A safety switch as claimed in any preceding claim, in which latching means are provided such that the actuator moves from the ON to the OFF position on successive actuations when the control member is in said second position.

6. A safety switch as claimed in any preceding claim, in 12 which the safety switch comprises a micro-switch incorporating a pair of electrical contacts, the state of connection between which changes between said OFF condition and said ON condition, and a switch member which is actuable to change the state of electrical connection, wherein the control member carries a projection which is displaced by the actuator in said ON position to actuate the switch member when said control member is in said second position.

7. A safety switch substantially as herein described with reference to Figures 1 to 5 or Figure 6 of the accompanying drawings.

8. A tumble drier incorporating a safety switch having an OFF condition and an ON condition, an actuator moveable between OFF and ON positions, and a control member movable between first and second positions, wherein the control member and actuator co- operate to only permit the switch condition to change from OFF to ON when said actuator is in said ON position and said control member is in said second position, and wherein the switch condition is changed from ON to OFF either when said actuator is moved from said ON to said OFF position or when the control member is moved from said second position to said first position.

9. A tumble drier as claimed in claim 8, in which the actuator extends through a front panel of the drier and forms a START/STOP button for the drier.

10. A tumble drier as claimed in claims 8 or 9, in which the position of the control member is controlled by the position of a loading door of the drier, the control member being in said first position when the door is open and vice- versa.

13 11. A tumble drier as claimed in any of claims 8 to 10, in which the control member is actuated by a projection on the door which engages the control member when the door is closed.

12. A tumble drier as claimed in any of claims 8 to 10, in which a catch retains the loading door of the drier in its closed position, the catch being arranged to release the door when a predetermined force is applied to the door in the door opening direction.

13. A tumble drier substantially as herein described with reference to Figures 1 to 5 or Figure 6 of the accompanying drawings.