Quick release mechanism electrically operated? 3

[Ktysai]

Hi there

I've come here after a heavy unlucky browsing looking for a quick release mechanism. Any hints are most welcomed, honestly I do not know where to look. It's not something complicated, but it has gave me a lot of hard time. I've searched the forum for some ideas, but nothing to fit the profile.

Basically the application involves a linear motor that needs to be coupled to an axle. The axle has at one end an compression spring. After the linear motor and the axle have been coupled, the spring is compressed.

An now it's the problem: I want to release the axle at various spring loads, so I guess a quick release mechanism electrically operated will do the job. But I haven't found any, well almost any...

The beneficiary of this mechanism will be a mobile robot, that will be more than happy to finally be able to walk or better say jump

The actual solution involves a quick release mechanism for hydraulic fittings (see the pic, only that it's modified a bit to need less coupling force) , but the release it's possible in just one position (where I put the limit claw that makes the coupling to be separated)

The spring will have maximum load around 40N and the coupling mechanism should be light and at most 20mm diameter.

I've tried to use an electromagnet, but for this holding force is too bulky and heavy. Honestly now I'm working at a solution that will make Frankenstein proud: to actuate the quick release in the pic with a little servo used in hobby RC servo

I find it a little odd to find all kind of solutions coupling circular moment, but very few regarding linear movement. Just point me into the right direction, 'cose for sure these days had made me crazy

Oh, it' just like a man want to buy shoes in mall: only women sandals are there

If you know companies that build such devices write a PM is cannot be put on the forum.


Thanks for taking the time reading this!


It's nice to be important, but it's more important to be nice!

 

[saplanti]

Please do not get me wrong, but the electrommagnet option is the most suitable one. How about trying to reduce the magnet force by introducing seperate mechanism such as leverage. Magnet might be on the longer side of the leverage and magnet force will be reduced. I do not know the space available and suitibility of the idea to the robot, but this idea might be used if the conditions are adequate. If the robot jums and the leverage on the way to the motion this mechanism might also be causing problem. Please accept this as a brainstorming.

 

[Ktysai]

Hello saplanti

Thanks for sharing your ideas!

The electromagnet idea is very appealing: it's clean and sexy. But from my calculation... it's not.

Here on the forum maybe I can find some info regarding electromagnets and verify by results. I'll have a try: at least now this idea has one more supporter

The robot is kind of spherical one with 12 legs, radially disposed this makes thing more challenging.

I do not understand the leverage mechanism idea. Can you elaborate, please?

I need suggestions, the one neuron I have left is still able to understand something

It's nice to be important, but it's more important to be nice!

 

[saplanti]

Assuming the legs are acting in the axial direction only, the quick acting can be done by the spring(s). Think about a lifting mechanism with a lever that load is on the short side and acting force on the long side. Assume load side is the compressed spring side and the load balanced by the magnet on the other. You will reduce the load by the ratio of the long lever length to short lever length; fundamental principle of Physics.

But, after finding out you will use 12 legs and each leg shall be activated the same way, this idea might be very difficult to implement due to the space requirement for the magnet side and the pivots connected on to the body or each leg by depending on the required locations of spring(s).

Of course the size and the mass of the robot are the major driving factors. I am not sure if you can reduce the mass. Changing materials might be an option if possible.

How are you going to activate the electromagnets in the system? Is the robot going to be electrical and a cable attached all the time? Is it going to have solar power (size might be problem) or batteries( mass and size are be large)? There are a lot of unknown in your project for us. Actually you are the best person to answer them all together and find the optimum solution.

I suggest you to look at the book called "Mechanisms and Mechanical Device Sourcebook" for selecting the suitable idea for your case. It includes the robot mechanisms as far as I remember.

It is too late now. I need to go to bed before I start sleeping in front of the monitor. Good luck.

 

[Ktysai]

With a lot of limitations the robot will have 1,5-2Kg fully electrical with rechargeable batteries. Is practically a sphere with a radius of 15cm with 12 legs getting out of it.

It's pretty tiny space in the center around the legs there's some space but the mases should be balanced.

I'll double check the electromagnet solution to be on the safe side.

The book you've recommended and another one is already on their way, hope to found something useful.

Have a good night and thanks again for your input!

It's nice to be important, but it's more important to be nice!

 

[alansimpson]

I think the mechanism you need is a "hair trigger". That is a device that will release the energy of the spring rapidly with very little energy input. I'm afraid I can't think of any products available. There are some small clapper electromagnets on the market but you would have to engineer your system carefully to avoid the system sticking.
If money is no object linear servo motors have a good power to weight ratio. Look up Linmot. or Trilogy. See also voice coil actuators, cheaper than servos but better than electromagnets.

 

[Lakey]

Suggestion: A permanent magnet (such as a neodymium) could be utilised to keep your spring compressed. If a coil was wound around the magnet, the magnet could be momentarily demagnetised when current flows through your coil - thus releasing your spring.

Regards,

 

[hendersdc]

Just a suggestion that might take a lot of work to figure out the details but what about a rotating cam to compress the spring? The same motor that rotates the cam could control the compression and release. Obviously not all the spring energy will make it into the jump action so the springs would end up being larger than with other methods.

 

[Ktysai]

alansimpson can you sketch the hair trigger, I'm ashamed to say that I haven't find a drawing. Only if it's not too much trouble. The voice coil actuators are interesting to actuate the device, I need to watch them closely. :->


Lakey You mean to find a small permanent magnet that can hold a 40N load and when I want to release it to energize the coil wrapped around the magnet? I think I've seen something similar for security doors. I'm not sure if I can block most of the magnetic force with the coil. Do you have some hint for computing this. Your suggestion has one big advantage: electrical current is needed only when detaching. Sweet!

hendersdc I know what you mean. One of the earlier designs was based on your idea. I've abandon the idea because of some technological problems and necessary space vs useful force.


Please share your ideas, as saplanti it's a brainstorm after all, even if I'm grumpy and ...

In any case I appreciate your input, it takes valuable time just to read the thread, what to say about sharing an idea.


It's nice to be important, but it's more important to be nice!

 

[zekeman]

Maybe you should post the picture you referred to in your OP.
I didn't get it.
There are a host of solutions but I need a picture.

 

[Ktysai]

@zekeman My bad

Here is the fast coupling. Is not the exact type but it's close

http://vivio.wordpress.com/primary-solution/eva44e307d4b3db9/

And here's a part of one article where we present the robot:

http://vivio.files.wordpress.com/2009/06/little-robot.pdf

Look at part 6 (Stop) and 9 (fast coupling). I've used first a fast coupling used in pneumatics, but after 20 cycles is dead. Instead on th the plastic coupling I have a metallic one, much more resistent. But if I change the whole thing, It would be a nice feature to make decoupling any time I like.

It's nice to be important, but it's more important to be nice!

 

[zekeman]

Have you looked at the design of an automatic center punch? Maybe you can get some ideas if you have to design it yourself.

 

[Lakey]

Hi Ktysai,

Yes, that’s correct.

A Neo. magnet (3/4” Dia. x 3/16” thick) should provide a hold in excess of 90N. A 1000 ampere-turns coil should destabilise the flux sufficiently for the release of the spring mechanism.

The actual size of your magnet and coil will depend upon your application and should be resolved by experiment.

Best regards

 

[alansimpson]

Looking at design cant think of products that may do job. Looks like a special design based on the quick release you already used. Other ideas based on "release hook" as used in pile driver or similar.
There may be a holding electromagnet configuration available but this would require power to hold.

Traditionally pneumatics would be used in a device of this configurations. This would require heavy umbilical of pneumatic tubing.

Take a look at "stock drive products" "Berg Precision" or Automotion. May have some suitable hardware.

 

[Ktysai]

zekeman pretty cool tool I must say, problem is that it's turned on at specific force. In wikipedia there was an example with a skewed pin, a little bit hard for me to manufactured it. Just of the record, I wanna buy this tool for my father, he's gonna love it. ;-) Thanks for showing this.


Lakey thanks for the aditional info. Can I get your atention again a little bit?

1. From where you've got those values? Can you help me out with some formulas? It tooked me some time to find some useful equation for electromagnet holding force. I know that the problem is not simple, I just want a little more human formulas

2. Let's say I want a maximum holding force of 50N.

2.1 I load the spring with 20N, so I have 30N until I can break the magnetic coupling with excesive load
2.2 I have to destabilise the Neo. magnet. Since the spring is compress 20N, I have to beat 30N with the electromagnet, right? For that I must build an electromagnet big enough to hold 30N and to put it in a way it can reduce the NEO. magnet force? Or the electromagnet can be smaller becouse it acts more directly on the NEO. magnet and not on the holding plate.
2.3 If I'm right I have to use a bigger electromagnet if I want the load to be relesead at smaller spring compression rates. That's correct?


alansimpson I'm going to look at those products. The thing is that I have the linear motors already and I must deal with that :-( I though the quick coupling should do the thing, but it didn't. I'm way behind my schedule, stressed and no quick way out.

A pneumatic cylinder will do the job, but will raise other problems regarding stroke control. All around me at work love pneumatics and hydraulics and I'm the one floating against the current using electric devices. I need to show them I'm right

All the best!

It's nice to be important, but it's more important to be nice!

 

[Lakey]

1. I had provided those values from experience. You can find all the formulae you need on Wikipedia or , for example,

http://www.magnetapplications.com

The formulae will get you so far, but there is no substitute for the actual tests that must be performed.

2. I’d guesstimate that an ½” Dia X ¼” NdFeB magnet would do the job. You can adjust the maximum hold by means of an artificial air-gap, such as a stainless steel or brass shim.

Once you’re satisfied with the ‘hold’ you can begin the tweak the needs of the coil. As mentioned, the coil only requires enough power to disrupt the magnet – anymore is a waste.

2.2 I suggest that you make a bobbin and then wind the wire onto that, so this assembly will slide comfortably over your magnet. I wouldn’t confuse this device with an electromagnet – I suppose the device in question is the opposite of an electromagnet, but we don’t want to be drawn into a discussion about terminology!

2.3 It depends - all things are relative! You will probably have to balance your design around the power of the available magnet. Note the grade of the magnet because if it’s overheated it may become useless.

You need to conduct your tests to find the best balance.

Good luck & regards,

 

[bill7853]

Does anyone know where to purchase electro magnet capable of pushing or repulsing another magnet 1" diameter a distance of 1" to 2" ?

 

[handleman]

1.Please start a new thread to discuss a new topic.

2.In that new thread, please provide the required additional information to solve the problem.

-handleman, CSWP (The new, easy test)

 

[waross]

Try playing with a couple of circuit breakers. Many of them use a collapsing toggle mechanism. It takes quite a bit of force to reset a circuit breaker. (Think molded case breakers, 100 Amps to 1000 Amps.)
The tripping toggle rests against a stop just a degree or so past center. A force that is extremely small in relation to the force of the main spring will move the toggle past top dead center and allow it to collapse and release the stored energy of the main spring to open the breaker points.
Look for an old breaker to play with. Take the cover off and use a rod to move the common trip bar.
[red]DON'T PUT YOUR FINGERS INSIDE THE MECHANISM. USE A TOOL OR ROD TO TRIP THE BREAKER.
THE STORED ENERGY IN EVEN A SMALL BREAKER CAN DO SERIOUS DAMAGE TO A FINGER. A LARGE BREAKER IS CAPABLE OF REMOVING PART OF A FINGER.[/red]
Examine a few old breakers to get a feel for the action and then work on adapting the basic principles to your project.
You will find a very, very large ratio between the stored energy force and the tripping force. I understand that this is what you are looking for.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Bill,

You'd love the stored energy actuators on the big SF₆ breakers.


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If we learn from our mistakes I'm getting a great education!