electric latch

Hi I have a one touch electric can opener (that no longer works). How it (used to) work:

-Place on a can

-Press switch (momentary) From there on it turned and cut off the top of the can and stopped when finished. I curious about how it worked. Specfically: How does the momentary switch "latch" or stay closed. (There aren't any electronic ics). Batteries then turn gears till the cutting is completed. Somehow a gear (I think) breaks the circuit and opearations is ended. The entire circuit is 2 AA batteries (3 volts), a motor, gears and switches. No electronics or digital logic. Thanks BobP

Reply to
BobP122
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Probably a "zero seeking" mechanism like a car windshield wiper motor running in "interval" mode. In that case a momentary (electronic) contact starts the action then a cam allows a switch to close latching it on. It stays closed until the wiper reaches its resting/storage position when the cam opens again shutting off the motor.

Reply to
default

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If it was cam operated, then it wouldn\'t work on different sizes of
cans.
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Reply to
John Fields

Maybe the motor current keeps the switch closed until the torque drops off. A simple magnetic thing could do that.

John

Reply to
John Larkin

Years ago I took one apart, there were no electronics in it.

What it did was the button would push in a gear that had a spring behind it to push it back out to unmeshed the gear.

Constant torque would keep the gear pulled in the basket and also keep a contact closed.

when torque was lost, the gear would pop out..

It's possible the gear is worn out or the switch contact needs a little adjusting.

This is typical for home counter top types. You could also have a DC solenoid tied in series with the load that is pulling in a contact while there is enough current from the load holding the circuit closed.

This also could be integrated in the motor, if that is the case, you should have a 3 wire motor at a min. The momentary switch simply supplies power after this internal switch to get it started. The current load will then pull the contacts to get power from the other wire.

Reply to
Jamie

You are right.

Motor loading might be one way.

Reply to
default

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Might be; maybe the OP can post some pictures pf the thing\'s guts?

JF
Reply to
John Fields

Basically it is a very simple minded mechanism that senses the motor torque. The motor shaft or a gear shaft is free to slide back and forth about a mm or two and is spring loaded forward. The motor pinion or gear has its gear teeth cut on an angle so when driving a load the reaction force pushes the shaft back. A leaf switch (thin phosphor-bronze leafs) make contact when the shaft pushes back on them thus closing the circuit keeping the motor running. When the torque eases off, the loading spring pushes the shaft forward opening the switch. These things are never elaborate or complicated.

Reply to
Bob Eld

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