352
M. Fenchea
Because of the percussion interactions between the hammer and material, unbalances appear even if the rotor, from the dynamic point of view, is considered as
balanced. Obviously, this situation does not appear if the percussion is applied to
the hammer so that it annuls the percussion in the articulation [5]. This thing leads
to the considerations of the percussion centre through which the percussions in the
articulation are eliminated and so the work of the machine is not disturbed [6].
2 Percussion Centre of Hammer
The joint between the hammer and rotor is made through a plane articulation so that
the hammer makes a relative rotation motion in relation to the axis of the articulation.
It is supposed that on the articulated hammer in O, the percussion
P acts in point
A, due to the collision with the material particle. As a result, in O the joint percussions
P 1 appear (see Fig. 1).
If
H and
K o are the variations of the impulse and of kinetic moment in relation
to the articulation O, the laws of the collision [6] will be
Fig. 1 Percussive
interactions