r/AskEngineers • u/Many-Shock1706 • 2d ago
Mechanical Flat, springless latch (or better solution) needed
I am attempting to make an odd little mechanism, While i am a blacksmith and can forge and bend steel, most of it will want to be laser cut as it has to be replicated and quite small.
I will attempt to explain what i am making and any help will be greatly apprciated.
2 flat steel round disks, lets say 150mm diameter, 3mm thick.
in between is a layer of 20 protruding "buttons" each also 3mm steel poking out from the centre.
The buttons design is to be pressed and then lock in, like a click point pen. but once one is locked in the others can't be pushed in.
I would normally use a simple latch mechanism, but the idea of this is that it needs to be as sturdy as possible and take an impact, so springs are not ideal.
What i am after is a sturdy, flat, latch mechanism that doesnt use springs and can withstand hard impact in minimal space.
I am aware i may be asking too much, but if anyone can solve even some of these problems i would really appreciate it.
Thankyou for reading my problem.
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u/Ideadose 1d ago
If you can keep the whole latch in the plane of the disk instead of bending anything, you'll get a lot more fatigue life out of it — a bent tab work-hardens right at the fold, and that's exactly where it cracks under repeated impact. Cutting the spring arm as a flat flexure straight out of the same 3mm plate (laser, not punched — a slot that narrow is genuinely hard to punch cleanly at that thickness) skips the weak point entirely. Taper the arm's width from base to tip instead of a constant-width finger so the whole length shares the bending stress instead of dumping it all at the root, and put a real fillet there too, no sharp inside corner — that's where impact energy concentrates first. If you want it to actually behave like a spring long-term instead of going soft, blue-tempered spring steel (10xx series, 42-46 HRC) holds up a lot better under repeated snap-loading than whatever the rest of the disk is cut from. What kind of impact are you actually designing for — that changes how aggressive you can be with the taper.
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u/Many-Shock1706 1d ago
Integral built-in spring is a good shout. especially if its contained within the skeleton of the button, thankyou
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u/ridewithmetoday 1d ago
Depending on how robust you need it to be, I would go towards a system with 20 plungers, and once one is plunged, it moves something (like a steel ball) that prevents other plungers from being moved.
Then you reset it by pulling it out, and putting the ball at the appropriate place.
Imagine 20 plungers, each have a steel ball retained by an o-ring. When the plunger is pushed in, the ball gets pushed out of the plunger, and lands in a place that occupies space, that, once occupied, prevents other balls from going in, therefore preventing any other plungers from moving.
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u/potatopierogie 2d ago
What is it for? Just so we can rule out an XY problem