Design Question

[deeja]

I’m trying to figure a way to propel/drive a drawer; similar to a cash register that rides on slides a total of 4.5” with a weight of 5 lbs. The application requires both vertical and horizontal configuration. Currently I’m using a compression spring configured behind the drawer, but find that the rate is to much in the horizontal application. Is there a way to make the rate consent in both positions ie vertical and horizontal using some kind of gearing or possibly a different form of drive device?

 

[MikeHalloran]

Perhaps a drawing would help us understand what you mean by "horizontal configuration" and "vertical configuration".



Mike Halloran
Pembroke Pines, FL, USA

 

[TheTick]

There is such a thing as a constant torsion spring. It is a spiral, like a watchspring.

Also, look inside a stapler. Usually they have long springs with nesting coils.

 

[deeja]

I'm sorry about not furnishing a picture, but allow me to better describe the design. Imagine a drawer that is 12” long, by 6” wide and 2.5” thick. The drawer holds a weight that varies from 2 lbs to 5.5 lbs. Behind the drawer is currently a spring used to eject the drawer open like a cash register out 4.5”. Now imagine that drawer being placed in a vertical position where it is facing up with the full effect of gravity on it then imagine it facing horizontal, perpendicular to the gravitational force. The compression springs do not release their energy at a consent rate. The result is the drawer opens very rapidly at first then slows down, I’m trying to acquire a mechanical fix for using the spring while maintaining a consent rate of speed. The gas springs work well but do not conform to the design specifications. I’m thinking of running a treaded rod down through the middle of the spring and attaching a threaded guide to create a gear reduction to try and create a consent rate of speed for the drawer. I hope that helps. I appreciate your help.

 

[TheTick]

How about a rotational damper w/ rack?

 

[deeja]

I have looked at that, the only problem is the expense of a large production. I am trying to keep the project as simple and low cost as possible.

Do you see a possibility were I can attach a threaded rod through the spring attached to the drawer with variable treading. More closely spaced treads at top and further spaced threads at the bottom correlating to the rate to the spring. The closely spaced threads will create drag on the force of the spring while the further spaced threads would create less drag allow the spring to extend to it full deflection.

 

[unclesyd]

Could you use something like a gas spring for your application. If not alone use it to control the spring rate.

http://www.easylift.com/applications/applications.aspx

 

[deeja]

The gas springs work well, but will not conform to the design specifications.

 

[BobM3]

So when horizontal the spring force is reacted by friction and when vertical the spring force is reacted by gravity? If so, how about a linkage that applies a second spring to the drawer when the drawer is vertical? When horizontal the linkage moves the second spring out of the way.

 

[MikeHalloran]

The tiny rotational dampers that control the motion of CD drawers and cassette carriers are produced in huge numbers, and so can be had for very little money; like USD .05 or so, if you buy a bucketful.

I'm not sure they're produced in a size that's large enough for you, but maybe you can dissect a few and scale them up.




Mike Halloran
Pembroke Pines, FL, USA