Anybody, esp someone who is in manufacture, any idea why just about every washing machine I have come across stays locked when it has finished? Why does one have to wait, what seems an eternity, before you can pull the stuff out? What is going on in the mechanism during that eternity?
It is to ensure that the drum has stopped rotating, and that the water has drained out. Ostensibly to prevent the consumer suffering damage, but really to stop the maufacturer being sued. (I speak as the owner of 39, mainly commercial, washing machines).
AWEM
It's required so there's no way you could open the door when the drum is still spinning. The interlock has to work if the mains fails (which is why it's usually a non-electrical timer), and it has to work if the belt breaks (so it can't rely on the speed servo on the motor).
If manufacturers were prepared to go more complicated/expensive, I guess you could have a drum motion sensor with an electronic means to bypass the standard interlock so the door could be released sooner if there's still an electricity supply, but I guess they don't think they could sell this feature.
My Miele unlocks immediately it has finished.
It depends on the machine and its control system.
Those with basic electromechanical timers have a time delayed mechanism to release the door after the final spin.
I just bought a Miele for my parents. This one has an electronic controller and is a good deal more intelligent. The door can be opened during the cycle as long as the water level is below the door. After spinning, the door lock is released the instant the drum comes to rest.
Sounds cheap.
Yeah - they're horrid things made out of old Ladas.
Very useful features indeed. I'm always wanting to open the door during the washing cycle, and I hate to waste all those seconds when it's finished
cost. The cheap inaccurate mechanisms are cheaper.
Often a thermally operated devices is used, heated by a ceramic PTC (thermistor) element. These have a low resistance when cold, so heat up quickly, giving a quick locking action. The release action has to wait for natural cooling of the device after power is removed, and usually takes a minute or two (hardly "an eternity" - that's just an example of the watched kettle effect in action).
Helps if you forget something
It would be somewhat bad design not to take advantage of the sensors and electronics available.
The worst example I saw of this was on a Zanussi machine that remained locked for three minutes. There's no reason for that at all - crap design.
Some advantage in having our ancient Hotpoint...purely mechanical with no time delay - locks only when belt is moving (so, yes, a broken belt does expose the risk of opening the door before the drum has stopped).
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Pete L saying something like:
It's so you can't stick your head in and turn the kitchen upside down.
Thanks guys. It seems that cheap thermistors are the reason. I still can't see why the lock mechanism can't unlock when the spin motor stops. I can remember in my childhood having a spin drier. This one just spun until my Mum thought it had done enough. Then she just opened the lid. Using common sense she waited until the thing had stopped spinning then pulled out the stuff. So simple and not life threatening!
before
...mmm ... the Hoover Spinarinse I think ! There is a bigger commercial unit used in Launderettes that has a brake drum on the spindle that is mechanically linked to the lid hinge so it stops when opened. However with a large wet load they don't stop instantly. There have been one or two incidents where inquisitive toddlers have lifted the lid, put in a hand, and literally had their arm ripped off at the shoulder. For this reason I removed them from my shops when I bought them - I couldn't contemplate living with my concience should such a thing happen in one of my Launderettes.
AWEM
My parents' Zanussi is terrible in this respect. It's about 3 minutes after you switch the machine off, not after it finishes. So you have to go to the machine after the cycle has finished and press the knob IIRC to switch it off. Then go and amuse yourself for 3 minutes before coming back to open the door.
Are launderettes used as much as they were in the past? Still a good business?
Yep, the current (old) Zanussi is just the same.
An even older Hot Point had a mechanical interlock. There was a pecker hanging above the belt driving the drum, a cable ran from the that to the door handle. If you tried to open the door with the drum moving the the pecker touched the belt moved sideways this allowed the cable to move inhibiting the latch. I think there was also a solenoid interlock as well so you couldn't open the door with the drum full of water etc...
Yes and yes. That's what we have (nearly 13 years old).
bought
Yes and no ! Most of my customers are 'dinkies', (dual income no kids) who both slog all day in the city to be able to pay their huge mortgage, and cannot be fagged to do chores like washing when they come home. They use our 4 minute system (2 mins to drop off, and two to collect). I would expect that most of the customers have their own washing machines but not the time nor inclination to use them !
AWEM
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