Linear motion translated to rotational 8

[tobee11]

Hello,
I'm interested in learning about gears & mechanisms that translate linear motion to rotational motion. Specifically, I need to translate the motion of straight-line linear motion (essentially straight up and straight down) into rotation, but rotation that is perpendicular to the linear motion.
Imagine a pencil that is inserted through a doughnut. I want to move the pencil up and down. I want the doughnut to rotate in one direction when the pencil moves up & and the opposite way when the pencil moves down.
Apologies for the crude description; I hope it makes sense.

Thanks very much.

 

[dvd]

depending on the scale you need, a yankee drill:

http://toolmonger.com/wp-content/uploads/2006/12/yankee-saw.jpg

lead screw:

http://www.nookindustries.com/acme/AcmeMetricAvailability.cfm

 

[tbuelna]

tobee11,

Try a face or barrel type cam (doughnut) and follower (pencil):

http://www.ul.ie/~kirwanp/drumcamandrollerfollower.htm

Good luck.
Terry

 

[MikeHalloran]

I've seen it done, with hydraulic cylinders backdriving ballscrews. I think they may have been multiple- start ballscrews, specifically engineered to be backdriven.



Mike Halloran
Pembroke Pines, FL, USA

 

[desertfox]

Hi tobee11

If you can move the pencil to the outside of the doughnut so to speak a rack and pinion would do exactly what you want. See this link:-

http://www.flying-pig.co.uk/mechanisms/pages/rackandpinion.html

desertfox

 

[Occupant]

In addition to the rack and pinion add a bevel gear set and you are in business.

 

[unclesyd]

How about a plunger spinning top.

http://gyroscope.com/d.asp?product=RAINBOWTOP

 

[MikeHalloran]

In short, it can be done.
Now you need to specify a load and a speed, so you can start the actual engineering.



Mike Halloran
Pembroke Pines, FL, USA

 

[tobee11]

Hello,

Thank you all for your responses. It is evident that there is a solution out there for me. A few more details:

The "doughnut" from my example is 3" in diameter and made of 18 gauge steel.

The doughnut needs to be able to rotate (on a plane that is perpendicular to the up-and-down action of the pencil) only 1". When the "pencil" is pulled down, the doughnut needs to rotate, say clockwise, 1 inch. Then, the pencil would be pushed back up and the doughnut would rotate back 1" to its starting position. That is the only motion I need. If the range of the up-and-down pencil motion can be restricted to less than 1", that would be ideal.

The up-and-down motion of the pencil will not be significantly repetitive. It's default position would be "up" and it will only be pulled "down" for a moment (basically rotating a switch to the closed position) before being returned to the up position.

The load is fairly negligible. Pulling down roatates a 3" diameter circle of 18 gauge steel 1" so that it locks onto a neodymium magnet. Pushing back up rotates the steel back to the starting position, but it will be fighting against the force of the magnet.

I hope that is clear and makes sense. Any more suggestions or advice you guys can offer me is greatly appreciated.

Thanks!

 

[dinjin]

Since the circumference is 3 pi, the rotation thru a complete revolution would be 360 degrees equals 3 pi.
So 1 inch of upward or downward movement would cause the disc or donut to turn 360 degrees divided by 3 pi
or 38.19718634 degrees.
Is this what you are looking for?

 

[itascot]

Hi all,

I'm new to this forum, but, have you considered using an actuator ? seems like the "pencil" movement is the same as a rising stem valve & "doughnut" seems like multi-turn actuator.

 

[tobee11]

Hello – I’ve looked at my project again and think there are a few more details I should share:

There is very little space above the “doughnut” (no more than 1/16th”). Therefore, the “pencil’s” up and down motion would have to occur below the upper plane of the doughnut.

The mechanism I am in need of will be part of a hand tool. The doughnut is essentially a switch. As it rotates in one direction, it would open a pathway between a magnet and a piece of metal, thereby allowing for connection. When it is rotated back, it would close that pathway, thereby releasing the connection.

Since the mechanism is part of a hand tool, any components need to be small and durable.

Thanks again for all the comments so far. Any additional help and suggestions are greatly appreciated.

 

[desertfox]

Hi tobee11

It might be better if you can put a sketch on here, a picture speaks a 1000 words.

desertfox

 

[unclesyd]

Following up on the the post by itascot you need to get hold of a "Scripto Mechanical Pencil" and look at the mechanism. Also if you can find a cutaway of an "Stockham Wedgeplug Valve" there is a very compact mechanism that raises and rotates the taper plug.

Anecdotal:
The mechanism for the Scripto Pencil and the Wedgeplug Valve were designed by the same person. I got to work with him when I started to school under the CO-OP plan, a long time ago.

 

[tobee11]

Hello,

I have attached a very crude sketch of my system. I hope it is clear enough to convey the idea.

There are (2) sketches of the top-down view. One shows the system in it's open position (pathway between magnet and steel clear). The other shows the closed position (disk rotated so that it interfers with the pathway between the magnet and steel, thereby releasing the connection).

Thanks Unclesyd for the "Scripto Mechanical Pencil" and "Stockham Wedgeplug Valve" recommendations. I haven't found anything definitive yet, but will continue looking.

Thanks again for all of your help.

 

[desertfox]

Hi tobee11

I assume the 'U' shape around the bottom and sides, which appears connected to the central stem, all drops vertically 1" and at the same time rotates along with top disc (which also drops 1" vertical) to cover the magnet in closed position.
So where is the prime mover? ie:- is it the magnet or is there some other means.
The mechanisms that have been suggested mine included need an external force to get them moving.

desertfox

 

[tobee11]

Desertfox,

The 'U' shape can be considered a type of "sleeve" which surrounds the central stem. The sleeve and central stem are actually part of a handle. This component is part of a hand tool and the sleeve would be pulled down by the operator. The sleeve would be pulled down (appx 1 inch) and the top disc would rotate (appx 1 inch). There will be no room for the top disc to move up or down. It's motion will be restricted to rotation about the central axis. When required, the operator would then push the sleeve back up to its starting position, thereby rotating the top disc back to its starting position.

I hope that makes sense. Thanks again for all the great help.

 

[MikeyP]

Sounds like the ratcheting screwdriver idea given as the first response to your question would be ideal.

M

--
Dr Michael F Platten

 

[desertfox]

Hi tobee11

So the central core is joined to the cover but not to the top disc, but as the cover is pulled down the central core is meant to rotate the top disc I presume?
So therefore as MikeyP points out, the ratcheting screwdriver looks like your best option.
What I can't see on your sketch is any bearing support for the top disc, so what holds the top disc in position.

regards

desertfox

 

[tobee11]

Hi Desertfox,

The top disc is connected to the sleeve by the rod which runs down the middle of the central core. The top disc/rod/sleeve are not one piece, obviously, but in my mind they are the up and down/rotating system and the central core is just a foundation providing stability.

I also think that the Yankee, racheting screwdriver looks like a good bet. However, it seems I would have to have components custom made in order for it to work. Im afraid that would be cost prohibitive, so it looks like I'm going to have to go with a rotating "sleeve" connected to the top disc. The operator will rotate the sleeve and the top disc will rotate along with it. It wont be ideal, but it should get the job done and (hopefully) be simpler/less expensive.

If you have any additional suggestions, I would be very greatful. If not, then thanks again to everyone for all of the comments and help. I really appreciate it.

Tobee11