Non-cylindrical Dynamic Seal?

[Aconcagua]

I am designing a linear actuator. I would like a dynamic seal between the piston and the bore (IP66), but the piston will have some torque on it as it slides, so a cylindrical design won't necessarily stop it from rotating. Putting a flat on the piston would stop it from rotating, but I'm not sure how to design the seal groove then, or what seal to use. Does anyone have experience with non-cylindrical dynamic seals?

Thanks!

 

[BrianPetersen]

Design the anti-rotation feature separate from the cylinder so that the cylinder and piston rod can be round. Google "guided cylinder" - like that.

 

[Aconcagua]

I'm very space constrained on this and I was hoping that I could forgo another alignment feature.

 

[hendersdc]

Would you have space for two smaller cylinders?

 

[SwinnyGG]

Is this actuator double acting?

If not, put the d-flat on the shaft and guide it in the housing, and leave the piston round.

 

[Aconcagua]

No, I don't have space for two cylinders, and it is double acting. I realize I could have a anti-rotation feature and then a cylindrical seal (in series), but each requires a full travel length of length added onto the actuator.

I maybe able to use a keyway and a wear ring, because it probably only needs to be IP66. So I may not need to fully seal it.

 

[SwinnyGG]

How cost sensitive are you, and how much torque do you need to absorb and for how long?

Making the cylinder and piston oval or trilobular adds various amounts of torque capacity and allows you to seal with conventional materials and geometries. The only penalty is a cost increase.

 

[drawoh]

Aconcagua,

If your dynamic seal follows your flat face, the seal controls your rotation, sort of. Is that acceptable to you?

Unless someone here actually has done this, you are going to have to build a prototype and test it, and then test it again. What are the consequences of your device not meeting IP66?

--
JHG

 

[hydtools]

Add a fixed rod inside the cylinder parallel to the cylinder rod and passing through the piston.

Ted

 

[bluesman0007]

hydtools,
You beat me to it, have done this several times when space is limited.

SolidWorks 2013
Dell Precision T3500
Nvidia Quadro 2000
Dual Monitors