We are working to design a lock mechanism and need to hold a square plunger out of a hole for extended periods of time (potentially years). The square plunger is under pressure from springs to return to the hole. Initial testing with a friction pawl has been positive, but we wonder about maintaining grip over a longer period of time. The pawl is lightly spring actuated to maintain forced contact with the plunger surface at all times. Does anyone have experience with friction pawls and in particular why these are not as commonly used as ratcheting pawls? They seem to grip quickly and if angled correctly seem to hold on. Are there pitfalls we are not aware of over the longer term? Thank you for any thoughts.
Doesn't a boating cam cleat work in that fashion?
Image source: Schaefer Marine.
The harder the rope is pulled (to the left) the tighter the cleat bites it. If you can do the same with your friction pawl it too will lock onto the plunger even with wear over time.
The other device that comes to mind is the Sprague or one-way clutch.
Image source: SUMA Clutch and Bearing.
On this one the roller bearings will bite if the inner ring turns clockwise and will freewheel if the inner ring turns anti-clockwise. (Note the increased clearance on the anti-clockwise side of each roller bearing.)