Looking for a part, does it exist?

[Averagesupernova]

I have a project in which I need to find a part that would work as follows:
-
Imagine a smooth steel rod that is for instance .5 inches in diameter. Now imagine a block with a hole in it that fits around this rod. This block needs to slide easily and smoothly on the rod. However, sometimes I want to secure this block to the rod so it does not slide. It needs to be electrically controlled. At this point I'm thinking magnetic so it is just attracted to the rod. However, if it causes something inside the block to move and clamp to the rod that is fine too. This way the rod could be stainless steel or something non-magnetic. The duty cycle does not need to be 100%. Someone PLEASE tell me some type of device exists and point me where to find such a thing.

 

[FredGarvin]

I can't say I have ever seen or heard of anything like what you are looking for. The closest I can think of off the top of my head is a standard linear bearing/drill rod assembly with a hand actuated clamp.

Have you checked with any motion control specialists?

 

[Averagesupernova]

Of course, I would imagine something that doesn't exist. I have checked nowhere else at this point. It's something that popped into my head in the last hour or so as a solution. It NEEDS to be electrical. It will make enough on/off cycles for manual to be impractical.

 

[FredGarvin]

Just because I don't know of anything doesn't mean they don't exist. I'll keep an eye out and ask some folks in the morning too.

 

[Averagesupernova]

I find it hard to believe such a thing does not exist also Fred. I really appreciate your effort. I'll keep following leads here on the 'net. There are a lot of motion control companies out there but I'm just not sure what you would call a part like this. Some kind of brake maybe?

 

[Cyrus]

Just curious, how heavy is this block?

 

[Averagesupernova]

It doesn't need to be very heavy at all. It is used as an indicator and to actuate a switch.

 

[Cyrus]

How big a switch, like the one to flip on a light?

Also, what/how is it indicating?

 

[Averagesupernova]

It might not even be a microswitch. I will most likely make it optical.

 

[Cyrus]

Why can't it be fixed to the rod at some location, and the rod move up and down? It would be easier to clamp the rod at the base to hold the block.

 

[Averagesupernova]

The rod already moves. Up to 30 inches. The block can only be allowed to move within a 4 inch range. So it needs to slide sometimes. I really don't care to explain any more.

 

[Cyrus]

Top secret eh?

Well, without more information, it's going to be hard to know what's going on.

 

[Averagesupernova]

Well, you don't need to know any more about what is 'going on'. I'm tied to what I've already explained. There is no way to 'move this other part instead'. The rod moves. Sometimes the block needs to move with it, sometimes it doesn't. It never moves very far before releasing.

 

[Cyrus]

I don't know. Possibly an electromagnet?

 

[Averagesupernova]

An electromagnet. That's the assumption cyrus. However, has someone packaged up a handy little device that does what I described?

 

[Cyrus]

Nope, but I'll look online for ya.

 

[RainmanAero]

Hi Averagesupernova,

Well, you don't need to know any more about what is 'going on'. I'm tied to what I've already explained. There is no way to 'move this other part instead'. The rod moves. Sometimes the block needs to move with it, sometimes it doesn't. It never moves very far before releasing.

Just a suggestion: I (and I have found several other engineers) often have difficulty envisioning something described in words alone. Engineers live by drawings, and its why we always start a problem with (how many times have we heard this?) "Draw a Free Body Diagram".

From what I can gather from your write-ups it sounds a bit like an electro-magnetic solenoid might do the trick. This is a device with a solid core (through which current is passed) and the outer "block" could and would be the electromagnet. I know some solenoids with 1-2 inch throws, but I am not sure of 4 inches or more.

If you could do a simple drawing it might help us help you. A solenoid is a discrete (ON/OFF) device such that when you energize it the core is pulled to one extreme of travel and when de-energized a spring holds it at the other extreme. But if you want to be able to continuously vary the position of the rod through the block, then you might want to look at something like a jackscrew or an E/M piston. More power required to operate these devices, however.

Another question that could be important: What sort of external loads might be applied to either the rod or the block?

Rainman

 

[Danger]

If I were to build something to that requirement, I'd score the top of the rod with a ****load of 'v'-shaped serrations and incorporate a wedge-shaped solenoid plunger into the block.

 

[Averagesupernova]

I'm quite familiar with solenoids rainman. The would be device will ride on a vertical rod/rail. It is to slide freely until power is applied. Then it must clamp tightly onto the rod/rail. It is actually part of a motion control project. The would be device pulls an armature and squeezes the rod/rail or if it can just attract itself to the rod/rail strong enough to hold itself against gravity without actually 'clamping' the rod/rail then that is fine too.

 

[Cyrus]

So, something must be controlling this things up and down motion, or it will just fall. Why can't whatever is moving the block just stop?

Said differently, what is fixed and what is moving? The rod or the box. I take it the rod is fixed, and the block is moving, no?

 

[Danger]

Hey, Rainman;
Didn't mean to step on your toes there. I didn't realize that there was a page-2 when I posted.
Average (sorry, I forgot... that's Mr. Supernova to me ), you can also, if you want to, incorporate a brake caliper system into the block, which can still be applied by a solenoid. All that you need is to carve out a section of the block and replace it with a grabber.

 

[Averagesupernova]

So, something must be controlling this things up and down motion, or it will just fall. Why can't whatever is moving the block just stop?

Said differently, what is fixed and what is moving? The rod or the box. I take it the rod is fixed, and the block is moving, no?

Yes cyrus, something is controlling the rods up and down motion. That's part of the whole project. The rod moves. It has a range of about 30 inches vertically. The block can only move within about a 4 inch range. The block clamps down on the rod right before the rod is to move. When the rod stops, the block let's go. A weak spring will then pull the block up to the topmost position permitted by a stop. This distance that the spring has to pull is not likely ever more than about 4 inches. I had forgotten to mention the spring until now. Make sense?

 

[Averagesupernova]

Hey, Rainman;
Didn't mean to step on your toes there. I didn't realize that there was a page-2 when I posted.
Average (sorry, I forgot... that's Mr. Supernova to me ), you can also, if you want to, incorporate a brake caliper system into the block, which can still be applied by a solenoid. All that you need is to carve out a section of the block and replace it with a grabber.

I'm thinking along the lines of a brake caliper Danger but I'm hoping something exists already. Actually, I know for a fact that they do in the searching I've done in the last hour or so, but they are pneumatic and that is not an option for me. It is also important that a no electric current condition leaves the block loose.

 

[Cyrus]

Well, I'm of no use to you. Good luck in finding a solution.

 

[Danger]

they are pneumatic and that is not an option for me.

Maybe this is just because I'm used to jerry-rigging stuff (see my post in the Rube Goldberg thread in GD), but this doesn't seem like a problem to me. To start with, I'd build it myself... which doesn't seem to be an option in your case. Elsewise, though, why not just replace the pneumatic cylinder with a solenoid?

 

[Averagesupernova]

This is a production level project danger.

 

[RainmanAero]

Hi again,

OK, in reading your last few replies it seems clear to me that what you want is a linear Electro Magnetic Actuator (EMA). My former employer, the venerable Parker-Hannifin "gods" of electro-hydraulic actuation, have been investing heavily in developing EMA technology for aircraft because (duh!) it gets rid of the need for hydraulics. As such, since it is bleeding edge tech, you can expect to pay top dollar for it. But it is available:

http://www.yet2.com/app/insight/techofweek/7466

As I mentioned in my other reply, an assessment and analysis of the loads (static and dynamic) is in order to be able to size the EMA.

Rainman

 

[Averagesupernova]

Not even close Rainman. Please re-read this thread. The rod already moves on its own. I don't need a linear actuator.

 

[RainmanAero]

Look guy,

Not even close Rainman. Please re-read this thread.

If you're going to get snooty when I am trying to help you, then why don't you take my other advice and do a drawing? And to be snooty right back, I'd suggest you learn how to write specs. You'll need that talent:

The block clamps down on the rod right before the rod is to move. When the rod stops, the block let's go. (snip) Make sense?

No, to be honest, it doesn't. You say the block clamps down BEFORE the rod is to move. Then you say the block let's go when the rod stops. How about describing the motion itself because I am not understanding your description where it is only talking about a static block. Again, engineers work with drawings. I cannot imagine having to design a complex motin system based on words alone.

Rainman

 

[Danger]

This is a production level project danger.

I don't know what that means. Is it then to be something applied to a commercial product that your company will be selling? If that's the case, I'm outta here.