"The pattern of the laid-out conductor 2 may be varied to suit various purposes, for instance by altering the path of the conveyor 13, by shifting the positions of the protruding members 10 or by exchanging one component, such as a plate to which several or all protruding members 10 are secured, and the lay-out pattern of the conductor as shown in FIGS. 1 and 3 are merely intended to show various e" . . . .