GB2107383A - Door interlock mechanism - Google Patents

Abstract

A door interlock mechanism, especially for a washing machine, spin dryer or tumble dryer, comprises a catch (1) carried by the door (2), a movable latch (6,) carried by the cabinet and engageable with the catch to hold the door closed, a switch (11,) which need to be actuated to operate the machine, and a movable switch actuator (8) engageable by the catch when the door is closed and movable thereby into a position in which it actuates the switch and permits the machine to function. In the case of a washing machine or spin dryer means (24) are preferably provided for locking the latch (6,) in a position in which it prevents release of the catch (1), and hence the door (2) from being opened, when it would be undesirable or hazardous to do so. <IMAGE>

Description

SPECIFICATION Door interlock mechanisms This invention relates to door interlock mechanisms for use in machines of the kind incorporating a movable member arranged to be driven by an electric motor and enclosed within an outer cabinet fitted with a door for providing access to the member when the latter is stationary.

In such machines it is frequently desirable to ensure that access to the movable member cannot take place when the machine is operating and for operation of the machine to be prevented if the door is not properly closed.

According to the invention a door interlock mechanism in a machine of the kind referred to comprises a catch carried by the door, a movable latch carried by the cabinet and engageable with the catch to hold the door in the closed position, but capable of movement to a release position to permit the door to be opened, a switch which, with the door open, inhibits the operation of the machine, and a movable switch actuator engageable by the catch when the door is closed and movable thereby into a position in which it actuates the switch so as to permit the machine to function.

The switch actuator is preferably in the form of a lever pivotably mounted on or adjacent the latch so as to be rotated by the catch into a position in which it actuates the switch on closure of the door.

Preferably the actuator is disposed in a position so as to be not readily accessible to a user, and is so arranged that should an attempt be made to operate the machine simply by moving the latch, the actuator either inhibits such movement of the latch, or is itself rendered ineffective, such that the switch remains inoperative. Preferably the switch is mounted separately from the latch, so that movement of the latch, other than by the door catch or a special tool, carries the switch actuator clear of the switch.

The switch may be in the form of a plunger operated microswitch oran unbiased rocker switch, use of the latter having the advantage that the biased switch spring counter-pressure is eliminated, and thereby the need to provide an appropriate offsetting spring force.

The invention has particular application to washing machines, spin dryers and like clothes or fabric treating machines.

In such machines an interlock mechanism is designed to prevent the door from being opened when it would be undesirable or hazardous to do so, for example when the member is rotating, especially at high speed, as would be the case with the drum of a spin dryer or of a washing machine operating in the spinning mode, or in the case of a washing machine of the so-called "front loader" type, during a period of washing or drying in which the machine contains more than a predetermined level of possibly hot water.

For such an application locking means are preferably provided for positively locking the latch in a position in which it prevents the door from being opened, such locking means, at appropriate "safe" times, permitting the release of the latch and allowing the door to be opened. It will of course, be understood that a "safe" time is a time at which the door of the machine may safely be opened, for example when the drum of the machine is either stationary or is rotating at a suitably low angular velocity and, in the case of a "front loader" type of washing machine, when the machine does not contain more than a predetermined level of water.

Additional means can also be provided for enabling release of the latch, these comprising either an automatic arrangement operable at "safe" times, an indirectly operating arrangement including a control mechanism, e.g. a manually operable pushbutton or a solenoid-operated unit capable of releasing the door, or a directly operated arrangement in which manual pressure is applied to the door itself to release it.

An interlock mechanism in accordance with the invention can thus be designed to release the door, and either allow it to open under the action of an opening force, for example the pressure of a resilient door sealing gasket in the case of a washing machine, possibly supplemented by additional resilient means urging the door towards the open position, or to be opened merely by pulling on the door handle. The use of spring-loaded door opening latches or buttons, and associated baulking arrangements required to prevent operation of the latches or buttons during those periods when it is unsafe to open the door can thereby be avoided.

Thus the door release loading can be reduced to an extent that operation by a light duty solenoid is a practicable possibility.

Three different embodiments of the invention as applied to a front loader type washing machine, and a further embodiment applied to a tumble dryer, will now be described by way of example with reference to Figures 1 to 15 of the accompanying drawings in which Figures 1 and 2 represent a side view and a rear view respectively of one form of washing machine door interlock mechanism, Figures 3 and 4 represent similar views of an alternative form of interlock mechanism, Figures 5 and 6 illustrate an alternative form of door release arrangement for use in either of the embodiments described with reference to Figures 1 to4, Figures 7to 9 represent a side view, rear view and plan view respectively of a modified form of the interlock system illustrated in Figures 1 and 2, and Figures 10 to 15 show the operation of a further form of interlock as applied to a tumble dryer.

The mechanism illustrated in Figures 1 and 2 comprises a catch 1 pivotally mounted on the inside of the door 2 of the washing machine so as to be capable of partially rotational movement about a horizontal axis A, and biased upwards into a horizontally-projecting position, as shown, by a return spring 3. When the door 2 is closed the catch projects through an opening 4 in the front of the cabinet 5. Within the cabinet just above the opening 4there is located a vertically slideable latch plate 6 the lower end of which normally projects across part of the opening 4. Then, as the door is closed, the cam-shaped nose 14 of the catch makes contact with the latch plate 6, and is deflected downwards against the return spring 3.When the door 2 is fully closed the return spring 3 forces the catch 1 upwards to cause its nose to engage behind the latch plate 6 and, at the same time, make contact with a limb 7 of a bell crank lever 8 pivotally mounted on the cabinet and lying to the rear of the latch plate. This causes the limb 7 of the lever to be pivoted upwards about an axis B, and the other limb 9 of the lever to engage and actuate a switch 11 which permits the machine to be operated. The pivoting of the lever 8 also disengages a locking pawl 12 on the upwardly extending limb of the lever from a rearwardly projecting lug 13 on the latch plate 6.

All that is required to open the door 2 is for the latch plate 6 to be lifted, whereupon the door catch 1, and with it the door, will be released, moving away from the door opening 4 under the influence of the door gasket pressure. When this happens the latch plate 6 and the switch operating lever 8 will be returned to their original positions by light springs and/or gravity, thus re-engaging the locking pawl 12 and lug 13. Lifting of the latch plate 6 during a washing programme can be inhibited by any conventional means shown diagrammatically at 24.The inhibit mechanism 24 may, for example, incorporate a solenoid operated or a bimetal operated plunger arranged to prevent lifting of the latch plate 6 until completion of a washing operation, and a delay means may also be incorporated to ensure that the latch plate is held in the locking position for a sufficient time after current to the washing machine motor has been switched off at the end of or during a spinning mode to allow the machine drum to come to rest. Liquid detection may also be provided for preventing release of the latching plate when there is more than a predetermined level of water within the machine.

Release loading in such an arrangement is so much lighter than in machines having conventional forms of interlock as the latch plate, when operated, needs only to overcome the friction of its contact with the catch face brought about by the pressure of the resilient door sealing gasket when the door is closed. Accordingly movement of the latch plate to the release position may be achieved by means of a solenoid, for example as indicated at 15, activated either automatically by means of an electrical impulse at an appropriate time, or by means of a manually operable momentary contact switch.

However direct manual operation could also be used, preferably through some form of spring linkage to avoid overstressing the system should an attempt be made to open the door when this is prevented by the inhibit mechanism 24.

The arrangement can incorporate an electronically controlled release system if desired. Thus the electrical supply to the latch release solenoid 15 where this is provided, may be fed via a control consolemounted switch, and the low level side of a water level switch, as well as timer contacts, so that the door can only be released when the water level is low and the timer is in an 'off' or 'door release' position.

In order to provide a time delay so as to provide against the door 2 being released while the drum is still rotating i.e. running down, with all the other conditions having been satisfied, the release solenoid can also be fed via a power transistor or thyristor normally held in an 'Off' state by means of a voltage derived from rectified pulses from a tachogenerator driven by the washing machine motor, a capacitor with a controlled rate of leakage ensuring that the transistor orthyristor does not conduct until a fixed time after the motor has ceased rotating. With this arrangement the use of a costly and frequently complicated sensing arrangement directly responsive to the rotation of the drum, for ascertaining whether or not the drum is rotating, is avoided.

A separate locking mechanism as at 24 may also then be dispensed with.

The second embodiment of the invention is illustrated in Figures 3 and 4.

As in the case of the previous embodiment the door 2 carries a catch 1, but in this case the catch is fixed rigidly to the door. The switch operating lever 8 is also, in this embodiment, pivotally mounted on a pin C carried by the latch plate 6 itself. In closing the door 2, the cam-shaped nose 14 of the catch 1 urges the latch plate 6 and the limb 7 of the lever 8 upwards against a spring (not shown), and when the door is fully closed the plate asembly moves downwards behind the nose 14 of the catch 1, the latter then engaging the lever and causing it to operate the switch 11. An inhibit mechanism 24 is arranged to prevent upward movement of the latch plate 6 during a washing programme, when it is unsafe to open the door 2, as in the previous embodiment.

However when it is safe to open the door 2, and the inhibit mechanism 24 is not therefore operating, this can be achieved simply by pulling the door, and with it the catch 1 outwards, causing the latch plate assembly to move upwards by reason of the sloping cam face 16 on the door side of the nose 14 of the catch.

Figures 5 and 6 show an alternative method of automatically operating the door release mechanism. The latch plate 6 of the first embodiments is biased 'upwards' by a spring loaded locking member 22 connected to the latch plate at its lower end. The 'door release' state is thus the normal unstressed mode. A cam wheel 17 on the shaft 18 of a conventional timer holds the locking member 22, and hence the latch plate 6, in a 'downwards' position when it is unsafe to open the door, while during a safe period an appropriately positioned notch 23 in the cam wheel surface allows the member 22 and plate 6 to be moved upwards by a compression spring 20 to release the door catch 1.

This operation is immediately followed by the release of a spring-loaded return lever 21 actuated by an inner surface 25 of the cam wheel 17, to urge the locking member 22 and latch plate 6 downwards making it ready for the next door closure.

It will be understood that the terms 'upwards' and 'downwards' as applied to the embodiments de scribed relate to the mechanisms as illustrated, but that these can be disposed with other orientations if desired. For example the latch plate may be arranged to slide horizontally or at an inclined angle, the associated components being disposed accordingly.

Figures 7 to 9 illustrate diagrammatically a modification of the washing machine door interlock mechanism described with reference to Figures 1 and 2.

This interlock system similarly comprises a catch 1 pivotally mounted on the inside of the door 2 of the washing machine but in this case it is partially rotatable about a vertical axis, being biased towards a rest position by a return spring 3. When the door 2 is closed the catch 1 projects through an opening 4 in the front of the cabinet, as in the previous embodiments. However in this case the mechanism comprises a latch 6.0 formed in two parts 6.1 and 6.2. The first of these is approximately in the form of a rectangularframeslidablysupported in a housing H, fitted to the inside of the front of the cabinet.The housing H has an opening 4.1 which registers with the opening 4 in the cabinet, and the part 6.1 of the latch is located behind this opening 4.1 so as to be slideable horizontally between a locking position, in which an inclined projection 6.3 carried by the frame extends partly across the opening 4 and engages the nose 14 of the catch 1 when the door is closed, thereby preventing the door from being opened, and a release position in which it lies clear of the opening and permits the door to be opened.

The second part 6.2 of the latch 6.0 is in the form of a lever having a generally upright central section 6.4 with an upper and lower end sections 6.5, 6.6 respectively projecting at right angles from it as shown. The plunger P of a solenoid 15 is pivotally connected to the central section 6.4 near to its upper end which projects through an opening 26 in the upper wall 27 of the housing H, so that the upper end section 6.5 lies just outside the housing. A projection 28 on the central section of the second part 6.2 of the latch lies just inside the wall 27 and serves to locate that part of latch vertically with respect to the housing H.

The first part 6.1 of the latch carries a projection 6.7 terminating in a spigot 6.8 which engages loosely in a hole in the central section 6.4 of the second part of the latch.

On closure of the door 2, the cam-shaped nose 14 of the catch 1 makes contact with the cooperating inclined projection 6.3 of the first part 6.1 of the latch 6.0, and is deflected sideways against its return spring 3. When the door 2 is fully closed the return spring 3 causes the catch to return to its rest position, and its nose 14 to engage behind the projection 6.3, and, at the same time, make contact with a limb 29 of a bell-crank lever 8 pivotally mounted in the housing H. This causes the lever 8 to be pivoted in an anticlockwise direction (as shown in Figure 7 of the drawing) and another limb 30 to engage and actuate a microswitch 11 which permits the machine to be opreated. The pivoting of the bell-crank lever 8 also disengages an edge 37 of the limb 29 from a cooperating surface of the first part 6.1 of the latch 6.0.This allows the first part 6.2 of the latch 6.0 to be slid in the direction of the arrow A (Figure 8) when the second part 6.2 is pivoted in a clockwise direction with the edge 31 of the hole 26 in the wall 27 acting as fulcrum.

Opening of the door can be effected at an approp riate instant either, normally by energisation of the solenoid 15, or, in the event of a power failure, manually by means of a connection 38 to a suitable control which produces a pivoting movement of the second part 6.2 of the latch 6.0. This causes the first part 6.1 of the latch 6.0 to slide inwards and the projection 6.3 to release the nose 14 of the catch 1, whereupon the door 2 will be released, moving away from the door opening 4 under the influence of door gasket pressure, possibly assisted by an additional means urging the door outwards.When this happens the two parts 6.1,6.2 of the latch 6.0 will return to their original positions under the action of a spring 32 around the solenoid plunger P, and the bell-crank lever 8 will also return to its original position underthe action of a spring 33, thus re-engaging the edge 37 of the limb 29 of the bell-crank lever 8 with cooperating surface of the first part 6.1 of the latch 6.0 and securing it in position.

Movement of the latch 6.0 by the solenoid, or manually, during a washing programme is inhibited by a plunger 34 of an inhibit mechanism 24 engaging the end of the second latch part 6.2. The inhibit mechanism 24 arranged to be operated when the drum of the washing machine is rotating, or if the machine contains more than a predetermined level of water. As in the previous embodiments release loading is considerably less than in machines having conventional forms of interlock. This arrangement also has the advantage that the solenoid plunger only needs to move a small distance to disengage the latch 6.0 from the nose 14 of the door catch 1 and allow the door to be opened, as the distance moved by the operative end of the latch part 6.2, and hence of the part 6.1 is magnified due to the lever construction.

Manual operation is conveniently effected through a form of spring linkage to avoid over-stressing the system should an attempt be made to open the door when the inhibit mechanism 24 is operated to prevent this as in the first embodiment. A time delay may similarly be incorporated to prevent opening the door whilst the drum is running down after a spinning operation.

As in the previous embodiments also, the mechanism need not be mounted as illustrated but can have alternative orientations.

An unbiased rocker switch could alternatively be employed in any of the embodiments described in place of the microswitch 11, the shape of the actuator 8 being modified accordingly.

A further embodiment of the invention, utilising a rocker switch instead of a microswitch, and applied to a tumbler dryer will now be described with reference to Figures 10 to 15. The mechanism is otherwise similar to the embodiment illustrated in Figures 3 and 4, except that the inhibit mechanism is not now required and is omitted. The bell-crank lever 8 is replaced by a simple pivoted lever 8A one end 7A of which corresponds to the limb 7 of the lever 8 and the other end 9A of which is shaped to actuate the rocker switch 11 A. Figures 7 and 8 show the door of the tumbler dryer in the open position. Figures 9 and 10 show the door closed with the nose 14 of the catch 1 lifting the end 7A of the lever 8A against a stop S causing the other end 9A of the lever to operate the switch. As the catch 1 is withdrawn the slide 6 lifts with the pivot C and the end 8A of the lever 8A is held against the stop S. The rocker switch 11A is reversed to the OFF position, and the slide 6 returns under the influence of a spring (not shown), the resistance of the rocker switch allowing the lever 8A to rotate back to the position shown in Figures 7 and 8.

Claims (17)

1. A door interlock mechanism in a machine of the kind referred to comprising a catch carried by the door, a movable latch carried by the cabinet and engageable with the catch to hold the door in the closed position, but capable of movement to a release position to permit the door to be opened, a switch which, with the door open, inhibits the operation of the machine, and a movable switch actuator engageable by the catch when the door is closed and movable thereby into a position in which it actuates the switch so as to permit the machine to function.

2. A mechanism according to Claim 1 wherein the switch actuator is in the form of a lever pivotably mounted on or adjacent the latch so as to be rotated by the catch into a position in which it actuates the switch on closure of the door.

3. A mechanism according to Claim 1 or 2 wherein the actuator is so arranged that should an attempt be made to operate the machine simply by moving the latch, the actuator either inhibits such movement of the latch, or is itself rendered ineffective, such that the switch remains inoperative.

4. A mechanism according to Claim 3 wherein the switch is mounted separately from the latch, so that movement of the latch, other than by the door catch or a special tool, carries the switch actuator clear of the switch.

5. A mechanism according to any preceding Claim wherein the switch is in the form of a plunger operated microswitch or an unbiased rocker switch.

6. A washing machine or spin dryer incorporating a door interlock mechanism according to any preceding claim.

7. Awashing machine or a spin dryer according to Claim 6 including locking means for positively locking the latch in a position in which it prevents the door from being opened, such locking means, at appropriate "safe" times, permitting the release of the latch and allowing the door to be opened.

8. A washing machine or a spin dryer according to Claim 7, incorporating additional means for enabling release of the latch at appropriate "safe" times.

9. A washing machine or a spin dryer according to Claim 8 including a solenoid unit which is arranged to be actuated automatically at appropriate times to move the latch into the release position unless such movement is inhibited by said locking means.

10. A washing machine or a spin dryer according to Claim 8 or 9 including manual means for moving the latch into the release position unless such movement is inhibited by said locking means.

11. Awashing machine according to Ciaim 9 or 10 including resilient means which, on release of the door, urges the door open.

12. A washing machine or a spin dryer according to Claim 9 wherein at least part of the latch is in the form of a pivoted lever.

13. A washing machine or a spin dryer according to Claim 9 wherein the latch comprises a first part engageable by the door catch and a second part, mechanically coupled to it, in the form of a pivoted leverwhich is operable by the solenoid unit to move the first part into a release position, the locking means being operable to prevent pivoting move mentofthesecond part of the latch at times when it is not safe to open the door.

14. An interlock mechanism substantially as shown in and hereinbefore described with reference to Figures 1 and 2, or Figures 3 and 4 or Figures 7 to 9 of the accompanying drawings.

15. Awashing machine incorporating an interlock mechanism according to Claim 14.

16. An interlock mechanism substantially as shown in and as hereinbefore described with referpence to Figures 10 to 15 of the accompanying drawings.

17. A tumble dryer incorporating an interlock mechanism according to Claim 15.