friction stay hinge A motion control device for controlling movement of an operating member about a first axis and a second axis includes a main shaft including a hub and a control arm, wherein the hub defines a first axis opening.

The design principle of friction stay hinge:
The friction stay hinge manufacturer tells you that the device includes a cylindrical pivot member inserted into the opening of the first shaft, the pivot member being concentric with the first shaft. The pivot member defines a second shaft opening, and the device includes a cylindrical pivot pin inserted into the second shaft opening and concentric with the second shaft. The friction stay hinge manufacturers tell you that the main shaft is designed to pivot about a first axis in a first direction and rotate about a second axis in a second direction, wherein the first and second axes are orthogonal to each other. The friction stay hinge manufacturer tells you that in one embodiment, a hex traction spring is inserted between the pivot member and the main shaft to affect frictional resistance in one of two directions of motion.
The above is the design principle of friction stay hinge, I hope it can help you.