Rotary motion to linear reciprocating motion 1

[mworthi]

I need a cost effective way to convert rotary motion to a constant velocity reciprocating motion. This device will be used to level wind yarn samples for the carpet industry. The rolling ring linear drives by Amacol would be a great solution, but are over kill for this device. Another possible solution would be a mechanism like the level wind of a baitcasting reel, but cannot find a supplier for this type of shaft profile. I think this would be classified as a type of cylindrical cam.

 

[MintJulep]

We did this one about a year ago, search the archives.

"constant velocity" and "reciprocating" are mutually exclusive.

 

[Mandrake22]

Rack and pinion?
Constant angular velocity, after the ramp up from stopped, equals constant linear velocity.

 

[mworthi]

I found the previous post mentioned by MintJulep, and they were helpful. I needed to to state that the electric motor will not be reversing, and the mechanism has to be self reversing. The length of travel will only be 2 inches at a speed of approx. 20 ipm.Constant velocity after ramp up from stopped is exactly what I had in mind. Not all solutions meet these parameters.

 

[Dennyd]

mworthi,

Look in thread404-95728 and more specifically

http://www.kedacorp.com/cylindrical cams.htm

as mentioned by unclesyd in that thread. This takes you to a company that makes a wide variety of level-wind components.

Let us know what you settle on and why.

- - -Dennyd, P.E.

 

[arto]

Look in the "Ingenious Mechanisms" book - there might be something in there. From the same guys that put out Machinery's Handbook:

http://www.industrialpress.com/item.asp?BookID=10

 

[cilogistics]

hi
i am agree with mandrake22 as :

1.rack and pinion drive will be best for you.
OR
2.Device used in I.C.(RECIPROCATING) engine.(PISTON- CYLINDER)

But mainly it depends upon your application.

shil

 

[DLANDISSR]

mowrthi:
Thread winders usually employ a double thread type drive.
The thread goes both ways on the shaft. A follower rides in the thread and at the end of the shaft follows the thread to the return thread. This provides linear movement to distribute the thread evenly on the winder.

A fishing real is similar to the mechanism I have described.

Why not just buy a fishing reel and incorporate it into your design?

 

[Cockroach]

Scotch Yoke, as a mechanism you get pure rectilinear motion output from circular input. There are many varieties, all have the advantage of being very easy to machine or fabricate without the necessity of hobbing gears or relying on commercially available alternatives.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[ContraptionBill]

I have a related application that I've been thinking about. A rack gear for a particular machine is driven by two linked cranks driven at a constant velocity. The motor reducer outputs to a crank that rotates completely. It's joined to another crank that only rotates about 90° and reciprocates. That crank is on a shaft with a gear that drives a back and forth motion of a rach gear.
This company is plagues with maintenance issues associated with the bearings and drives associated with all the offset loads that the drive produces.
I've been trying to think about it from a clean slate. A hydraulic cylinder powering the rack gear seems stright forward, pneumatics are another technology, screw rollers would be too inefficient I think.
System requirements...the rack gear conpletes one cycle every 1.5seconds. The stroke is about 12". The driving force is nearly 1000lbs.
Their current system is driven by a 3hp 3ph motor through a 43:1 reducer and the cranks and shafts I've mentioned.
Space requirements have driven the current arrangement and no real changes have been made to it since it was first developed back in the 50s and 60s before hydraulics were as good as they are now.

Anyone have any opinions for me?

 

[MikeHalloran]

To wind yarn level, you need a level wind, hence the name. The rolling rings are underkill, because you can't repeatably tune them to the exact pitch you need, and you'll be 'fine tuning' them forever.

The requirements are not that difficult. The translation of the level wind has to be set up for the diameter or width of the yarn/ whatever, and it has to be mechanically linked to the takeup spool, so that the level wind carriage translates by exactly one product width per revolution of the takeup spool. The carriage has to reverse direction precisely, repeatably, and quickly, at each end of the spool.

All of that can be done with fancy motor drives available today, but by the time you get the takeup and the lateral drive phase- locked and the lateral drive repeating its reversals with any precision, it has to be cheaper to do it mechanically, even if the entire mechanism has to be custom made.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[Compositepro]

Level winding, where the strip is stepped over by a little more than its width for every revolution of the spool, does not require high precision in wind ratio but it usually requires an adjustable ratio so that different width strips can be wound. Flanged spools are often required to keep level-wound rolls from falling apart. The Amacoil traversing devices work very well for level winding.
Precision way-winding is often used for fibers to produce spools that are stable without flanges. The fiber may only make three to six wraps around a spool per traverse. It is the high helix angle that keeps the fibers from falling off the edges of the spools without using flanges. The traverse ratio has to be controlled though gearing because the ratio has to be precise to five decimal places or so to produce a decent quality package.
If you can live with only one ratio you can use a screw mechanism for traverse with a spring toggeled reversing gear. But it will be hard to beat the preengineered convenience and versatility of an Amacoil.