linear actuator mechanism

[freerangequark]

Hi,

In my spare time I am working on a toy invention. For the purpose of this invention, I need to create a mechanism as follows:

1. The mechanism must lift 8oz (item 1) over a distance of 8" in one second or less. item 1 must then rotate 30 degrees clockwise, then 30 degrees counter clockwise, then retract.

2. The mechanism must fit within a 4 x 4" footprint.


For these requirements I figured I would use a leadscrew with a guide to limit rotation during extension and retraction which would also allow the 30 degrees rotation only at the extension limit. The single motor would then be controlling the extension, rotation, and retraction, movements.

The leadscrew I will use would be a 3/8" Stub Acme thread with a 1" lead per rotation (5 starts). To get the extension speed I need, I need to turn it at 480 RPM which I figure I could achieve by gearing down a small high rpm DC motor with sufficient torque.

This is the first time I have needed to design a small toy type mechanism and was looking for some feedback on my approach.

Any help or suggestions would be greatly appreciated.

Thanks!

 

[zekeman]

Looks too complicated for a simple discussion. Not your garden variety problem.
Time to hire a consultant well versed in kinematics?

 

[GregLocock]

What does retract mean in this concept? drop the load again?



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GregLocock]

and what are your other constraints? minimum cost? life? toxicity? ease of use?

This reminds me of typical design problems set when I was at university.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[freerangequark]

"What does retract mean in this concept? drop the load again?"

It means, lower the load back to its starting position. It can be retracted, or it can be dropped. It just has to end up where it started


"and what are your other constraints? minimum cost? life? toxicity? ease of use? "


Cost - as little as possible. it's a toy that I need to be able to produce cheaply.

Life - 25,000 cycles

Toxicity - none since it's a kids toy. If if were a toy for politicians, I would say high toxicity.

Ease of use - automatic since the cycles is triggered by an event.

Also, I need to be able to power it with common household batteries.


Thanks you

 

[tripleZ]

Not sure about the 4 inch by 4 inch envelope, but I'd suggest browsing through teh PHD catalog. Tons of info on linear actuators, rotational actuators, gripper arms, and all the sensors you need to blow your allowance for the month. Unfortunately, these are air powered in many cases.

Are you limited to mechanical means, or is air an option? And what sort of "event" are you using to trigger the actuator/gripper? Are you tripping a switch to cause the circuit to fire, or are you looking for a sensor to dictate position, etc.? How 'bout geometry of the toy? If you've got to lift it, are you using mechanical grippers, magnetic means, air suction...take your pick???

 

[GregLocock]

ok, plastic lead screw in a post with a slot in it. Nut with a lever on a friction clutch sticking out through the slot. at the top of the slot widen it out o 30 degrees.

arm goes up, hits the open bit arm swings across hits reversing switch, motor reverses, arm swings other way, then the nut winds back down the lead-screw.

You need to have a hold-high relay or something on the motor circuit.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[freerangequark]

Thanks for the tips. It sounds like my idea is very similar to what you're describing. I'll have to start modeling this up.

Thanks!