Method of manufacturing cylindrical ceramic tubes having localized imprints on their inner faces

A method of making imprints on the internal walls of tube portions obtained by the continuous molding of a ceramics-based paste into a continuous tube and the cutting up of the continuous tube into individual tube portions, said method comprising the steps of:

• (a) while the tube portions are still deformable, placing the tube portions on a bed of driving rollers disposed on a horizontal support, the axes of the driving rollers being parallel to each other and in the same horizontal plane such that the axes of the tube portions are parallel to the axes of the driving rollers;
• (b) rotating the driving rollers about their axes in the same direction, thereby causing a translatory movement of the driving rollers, which roll without sliding on the horizontal support;
• (c) applying pressure-exerting means to at least a part of the tube portions so that the tube portions are clamped between the driving rollers and the pressure-exerting means;
• and
• (d) imprinting the tubular portions with at least one imprint-making tool provided on either the driving rollers or the pressure-exerting means, the imprint-making tool having a main imprinting direction which does not coincide with the direction of the axes of the driving rollers, by creating a relative movement between the tube portions and the imprint-making tool while permitting substantially no sliding between the tube portions and the imprint-making tool.