Roller assembly with roller retention mechanism

A roller assembly comprising:

• a body with a cylindrical bore;
• a single-use disposable roller retention mechanism located inside the bore, said single-use disposable roller retention mechanism being adapted to be removed before the rest of the roller assembly is placed in operation, a plurality of rollers extending lengthwise inside the bore, said rollers extending around the entire circumference of the bore with all the rollers in contact with the wall of the bore, said roller retention mechanism having at least three circumferentially spaced portions, each extending radially between two adjoining rollers to contact said two adjoining rollers in a manner to push these two adjoining rollers apart circumferentially to keystone all the rollers so that all the rollers in the circumferential space between the circumferentially spaced portions are in contact, all the rollers being pressed against the wall of the bore with sufficient force to prevent axial movement of the rollers, said rollers being prevented from falling radially inwardly into the center of the bore solely by the keystoning effect of said circumferentially spaced portions.