Storage mechanism with locking and unlocking

[magicfrog]

Hi everyone, I tried searching the forum but couldn’t find anything directly related.

I’d like your opinion on the existence or feasibility of a mechanism concept I’d like to explore. I’m attaching a rough 2D sketch and I’ll try to be as clear as possible.

Imagine a rod that must perform a linear stroke of about 40 mm (just an example). A compression spring is installed between a mechanical stop and one end of the rod. During the rod’s stroke, the spring is compressed and stores energy. The goal is to stop the compression at a specific position (for example at 20 mm), but then allow the rod to continue its remaining stroke while decoupled from the spring—so the rod can keep moving freely.

In my mind, this would be a nested mechanism (made of sub-mechanisms): initially, all components move together and the spring is compressed. Before reaching the target stroke “x”, a first mechanism deploys “hooks” (or a locking feature) to create a mechanical stop that keeps the spring compressed. Once stroke “x” is reached, a second mechanism disengages the rod from the spring, allowing the rod to continue its travel without feeling the spring force.

My question is: does a system with this behavior already exist? Can anyone point me to similar solutions or share insights? In other words, I’m looking for a mechanism that can store energy, hold it mechanically, and release it only under specific conditions.

The sketch is very rough since I don’t yet have a clear architecture, dimensions, or supporting data. Thanks in advance.

 

[magicfrog]

More specifically, the idea is to have a linear mechanical system that, during the forward stroke, activates mechanisms needed to:

1. store energy (compress the spring),
2. retain it (mechanically lock the spring plate),
3. disengage the rod so it can continue the stroke freely.

During the return stroke, the sequence would be reversed:

1. free travel up to a certain point,
2. re-engagement between rod and spring plate,
3. release of the mechanical lock,
4. spring energy discharge (with some form of controlled release/dissipation as needed).

I realize this is likely a complex mechanism, and I don’t yet have concrete ideas for an efficient way to implement these “nested” functions, but it’s definitely an interesting concept.

 

[Filip Larsen]

I am not a mechanical engineer, but I would imagine that for a purely mechanical device you will need some kind of latching function.

Perhaps you can be inspired from the soft close mechanism used for drawers. Or perhaps the similar but opposite function of push to open. I am not aware if these two both utilize the same mechanism or if it is two different approaches, but both sort of do what I understand you seek.

 

[berkeman]

Can the rod rotate 90 degrees at the hand-off point? If the rod can be rotated, that may simplify the engaging/disengaging of the spring hold mechanism.

 

[magicfrog]

I am not a mechanical engineer, but I would imagine that for a purely mechanical device you will need some kind of latching function.

Perhaps you can be inspired from the soft close mechanism used for drawers. Or perhaps the similar but opposite function of push to open. I am not aware if these two both utilize the same mechanism or if it is two different approaches, but both sort of do what I understand you seek.

I think that kind of mechanism is a push/pull mechanism. To enable the free travel, I need to push in one direction to release it in the other. Unfortunately, in my case I only have a linear stroke, with no possibility to implement a push/pull mechanism.

 

[magicfrog]

Can the rod rotate 90 degrees at the hand-off point? If the rod can be rotated, that may simplify the engaging/disengaging of the spring hold mechanism.

The rod can only translate linearly by a given number of millimeters. However, nothing prevents adding a collar that can rotate while the rod translates, so you can engage and disengage the mechanism. Were you thinking of a barrel cam?

 

[berkeman]

Were you thinking of a barrel cam?

Not specifically. I was picturing a way to disengage the rod end from the spring collar by rotating a key shape to that it frees up from the collar. The spring collar would be held by latching hooks at the position you want, until the rod comes back and rotates to engage with the collar and disengage the latching hooks.

 

[Filip Larsen]

I think that kind of mechanism is a push/pull mechanism.

Yes, something like https://www.tanerxun.com/push-to-release-mechanism-design-plan.html

I understand you think that won't exactly do what you want, but my points was 1) it sound like something along those line so maybe you can reuse part of the design, and 2) it probably cannot be done much simpler unless you want to add a separate manually operated latch mechanism.

 

[magicfrog]

Not specifically. I was picturing a way to disengage the rod end from the spring collar by rotating a key shape to that it frees up from the collar. The spring collar would be held by latching hooks at the position you want, until the rod comes back and rotates to engage with the collar and disengage the latching hooks.

Yes, I thought about something like that too. But how would you rotate the key? With an external action? Or always with a mechanism linked to its single linear stroke? Basically, it should be something reversible, in the sense that what happens on the forward stroke must also happen on the return stroke in reverse order.

 

[magicfrog]

I was thinking about a nested system of cylindrical cams. At least two driven by the same linear stroke of the rod. The outer one would rotate the collar and position it in a stop position relative to the spring thrust, and an inner one would decouple the rod in a second consecutive moment. In the return phase, I would have the coupling of the rod and subsequent decoupling of the collar with consequent spring thrust. But I think I'm missing something. I should make some sketches and understand the feasibility. Could it work??

 

[Averagesupernova]

Once stroke “x” is reached, a second mechanism disengages the rod from the spring, allowing the rod to continue its travel without feeling the spring force.

Unfortunately, in my case I only have a linear stroke, with no possibility to implement a push/pull mechanism.

Unless I missed something the discussion so far has been about a mechanism that after the rod is pushed so far, holds the spring and releases the rod from the spring. At this point the rod is free. What is it that returns the rod? Or is this a one time operation? You say you have no possibility of a push/pull mechanism so it implies the operation as you describe is finished.

 

[magicfrog]

I probably didn't express myself clearly, and I apologise for that.

Everything will be managed by an external action.

For example, I pull the stem to accumulate and store energy, disengage the stem and continue my run. I push the stem to engage it again, recover the stored energy and express it.