Spiral scissor lift statics

[carlcla]

TL;DR Summary: I need help to understand the concept for load absorbtion in a spiral scissor lift.

Hello everyone!

I have a mechanical engineering project for the end of this semester.

We have been tasked to design a spiral scissor lift similar to what’s in the attached picture. My question is regarding the statics. When the lift is stationary with a load on the top platform, are there any norms or guidelines for how much of the load will be absorbed by the scissor structure and how much of the weight will be absorbed by the spiral column itself?

I understand that when in motion, the spiral column has to be able to lift the entire load. But how about when its being static?

 

[Baluncore]

I understand that when in motion, the spiral column has to be able to lift the entire load. But how about when its being static?

The "scissors" keep the platform level in the long direction, while one or more torque tubes, between the two scissor sides, keep the platform level in the cross direction.

The spiral column, (that looks to me like a ball screw), must support the entire load, and the platform.

The scissors carry only differential moments, or torque loads, associated with keeping the platform level when the load is not applied above the column axis.

The column will still carry the entire load when static, unless the scissors can be locked, (at the 4 sliding points), to prevent movement at the top and bottom, and the spiral be released from the platform.

 

[Baluncore]

Not a ball screw, but a helical band actuator.
https://en.wikipedia.org/wiki/Helical_band_actuator
https://www.galasystems.com/en/spiralift/

 

[Lnewqban]

@carlcla
1)Could you please clarify your concept of “load absorption”?

2)Could you explain the reason to be and the function of the scissor mechanism in this case?

3)If the joint of the lifting mechanism to the top platform articulated?

4)How static balance would be achieved if we remove the scissor and leave the lifting mechanism in place?

 

[Lnewqban]