Suggested distractor mechanism, any help? 11

[Chaabain]

Dear all mechanical engineers,

I have a problem and I would like to know if you can help me to get a solution:

Our system consists of a fixed plate, a mechanism, and a mobile plate. When the force applied to the mobile plate is equal to Fa =150 N, the mobile plate is stable (Case 1). As this force decreases, the mobile plate must move upward till the applied force is once again equal to Fa (Case 2). The mechanism should be locked after this movement. What type of mechanism could we use to achieve this giving that the initial distance between the plates is 5 mm and the maximum allowed distance is 10 mm?

Illustration:

http://files.engineering.com/getfile.aspx?folder=ebb48677-a214-49b6-ba8e-53c60e5e539b&file=Idea.bmp

Thank you in advance;
Chaabain

 

[macthenife]

Window frame sealant guns use a very simple rod and lock plate to deliver linear movement and positional control.
In your case a helical spring fitted around the rod and between the plates would provide the saparating force.

The "unlock-reposition-lock"system would be controlled by a pressure sensor on the top plate actuating,by appropriate logic,a lock plate solenoid.

If you focus on the design of the lock plate you could reduce the actuating force to a level where quite a small battery could operate the system.