Bearer ring

The Schmitzring is part of the printing unit construction of modern printing machines .

Bearer rings on printing machines are arranged on the sides of the printing cylinder. The Schmitz ring should prevent Schmitz . It is made of tempered steel and is ground with high precision, round and true to size. The bearer ring is approx. 1–2 cm wide and rolls either on the foundation rail or on the bearer ring of the counter cylinder. The circumference of the bearer ring is exactly the circumference of the elevator including a printed sheet or it has exactly the circumference of the shape including the finishing behind the mold (finishing only in offset printing ), depending on which machine part it is attached to. The bearer ring is an element of forced guidance on machines with a central drive and compensates for minor bearing inaccuracies as well as uneven input and output from the gear drive of the printing machines (single-motor system). Bearer rings can also be found on extraction presses and on crucibles .

The bearer ring secures the register-accurate processing through friction inhibition . Bearer rings run on each other in the following areas (offset machine): plate cylinder - blanket cylinder, blanket cylinder - impression cylinder . In letterpress printing machines, bearer rings are also attached to the inking rollers, which are intended to ensure that the inking roller runs exactly on the form. If the roller is smaller or larger than the bearer ring or if the bearer ring can slip on the guide rail due to oil or grease, the mold will roll smoothly . Bearer rings can only function if they are clean, undamaged and under slight pressure. In the past and on slow-running machines (up to approx. 5000 Bg / h) bearers were dusted with talc and rosin powder to increase friction.

Bearer rings are often only used as moving spacer rings on modern printing machines. The designation Schmitzring is no longer entirely appropriate here. The necessary synchronization control of the unwinding cylinders takes place via an electronic element in the individual drive control. In this way, uneven lifts or partial oversize and undersize in the lift or the dressing can be compensated for, which a classic bearer ring cannot.