As shown in the treatment of direct contact bodies, this requires that the common normal to the surfaces not to pass through the pivotal axis of either the driver or the follower.

Said base, said lever and said pressing part can be assembled together actively through springs, so said lever can be assembled on the base rotating around the pivotal axis supporting said springs.

The pivot mounts allow the pivotal movement of the protective housing relative to the pivot mounts and about horizontal axis AA.