Method and apparatus for manufacturing an absorbent article

Method of making an absorbent article (144), the article comprising a liquid-pervious topsheet (121, 145), a liquid impervious backsheet (123, 146) and an absorbent core (120, 147) interposed between the topsheet and the backsheet, the method comprising the steps of:

• a) feeding a web (1), comprising the topsheet (121, 145) the backsheet (123, 146) or the core (120, 147) or a combination thereof along a stationary frame (35), along an upstream trajectory (3), a downstream trajectory (5), and an intermediate trajectory (7a, 7b, 7c) comprised between the upstream trajectory and the downstream trajectory, the web (1) having along the upstream trajectory (3) and along the downstream trajectory (5) a substantially constant speed of transport, the upstream and the downstream trajectory (3, 5) being substantially stationary relative to the frame (35),
• b) running the web (1) along an upstream and a downstream guide roller (9, 11) that are translationally stationary relative to the frame (35) and along an upstream and a downstream transport roller (13, 15), wherein the periodically displaceable transport rollers (13, 15) are connected to a displacement balancing means (77), such that:
• a first section (7b) of the intermediate trajectory (7a, 7b, 7c) of the web (1) extends between the upstream guide roller (9) and the upstream transport roller (13),
• a second section (76) of the intermediate trajectory (7a, 7b, 7c) extends between the upstream guide roller (9) and the downstream guide roller (11) or between the upstream transport roller (13) and the downstream transport roller (15), and
• a third section (7c) of the intermediate trajectory (7a, 7b, 7c) extends between the downstream guide roller (11) and the downstream transport roller (13),
• the first section (7a) and the third section (7c) of the intermediate trajectory (7a, 7b, 7c) of the web, (1) being parallel to the second section (7b) of the intermediate trajectory,
• c) periodically displacing the transport rollers (13, 15) relative to the guide rollers (9,11) around a stationary equilibrium position (39) at a frequency of between 1 Hz and 100 Hz, in a direction substantially parallel to the second section (7b) of the intermediate trajectory (7a, 7b, 7c) of the web (1), while keeping constant the length of the intermediate trajectory (7a, 7b, 7c) and while keeping constant the length of the second section (7b) of the intermediate trajectory, and
• d) moving the displacement-balancing means (77) so as to keep a combined center of mass of the transport rollers (13, 15) and the displacement balancing means (77) substantially stationary.

Apparatus (2) for manufacturing an absorbent article (144), the article comprising a liquid-pervious topsheet (121, 145), a liquid impervious backsheet (123, 146) and an absorbent core (120, 147) interposed between the topsheet and the backsheet, the apparatus comprising:

• a stationary frame (35),
• an upstream and a downstream guide roller (9, 11) connected to the frame (35) in a translationally stationary manner, each guide roller (9, 11) having an axis (19, 21), the axes (19, 21) being generally parallel, the guide rollers (9, 11) being rotatable around their axes (19, 21), the rotational drive means (50, 51) a drive member (50) which is run along guide rollers (9, 11) and the transport rollers (13, 15) to form a closed loop, and a drive motor (51) driving the drive member (50) at a constant speed and a constant direction of rotation,
• and upstream and a downstream rotatable, cylindrical transport roller (13, 15), the axes (25, 27) of which are generally parallel to the axes (19, 21) of the guide rollers (9, 11), the cylindrical surface of the upstream guide roller (9) and the upstream transport (134) roller being substantially tangent to a first plane (29), the cylindrical surface of the downstream guide roller (11) and the downstream transport roller (15) being substantially tangent to a second plane (31) which is substantially parallel the first plane (29), and a circumferential surface of both guide rollers (9, 11) or both transport rollers (13, 15) being substantially tangent to a third plane (33) which is located at a spaced apart location from the first plane (29) and the second plane (31) and which is parallel thereto,
• translational drive means (36, 71) connected to the frame (35) for periodically displacing the transport rollers (13, 15) generally perpendicular to the axes (25, 27) of the transport rollers (13, 15), around an equilibrium position (39) located generally midway between the axes (19, 21) of the guide rollers (9, 11), a distance between the axes (25, 27) of the transport rollers being constant,
• rotational drive means (50, 51) for rotating the transport rollers (13, 15) in synchronism with the displacement of the transport rollers, such that when a web (1) comprising the topsheet, the backsheet, the core or any combination thereof, is run past the transport members (13, 15), strain on the web (11) is not substantially larger than strain exerted on the web by inertia forces acting on the web (1), and
• rotation balancing means (63, 63') for each transport roller (13, 15) a rotatable disc (65, 65')a phase of the rotational speed of which differs by 180.degree., or a whole multiple thereof from the phase of the rational speed of the transport rollers (13, 15), so that the transport rollers (13, 15) and the balancing means (63, 63') in combination can be rotated at a constant torque.

Apparatus (2) for manufacturing an absorbent article (144), the article comprising a liquid-pervious topsheet (121, 145), a liquid impervious backsheet (123, 146) and an absorbent core (129, 147) interposed between the topsheet (121, 145) and the backsheet (123, 146), the apparatus comprising:

• a stationary frame (35),
• an upstream and a downstream guide roller (9, 11) which are connected to the frame (35) in a translationally stationary manner, each guide roller (9, 11) having an axis (19, 21), the axes (19, 21) being generally parallel,
• an upstream and a downstream, rotatable, cylindrical transport roller (13, 15), the guide rollers being connected to a sled (41) which is translationally mounted on the frame (35) the axes (25, 27) of which are generally parallel to the axes (19, 21) of the guide rollers (9, 11), the cylindrical surface of the upstream guide roller (9) and the upstream transport roller (13) being substantially tangent to a first plane (29), the cylindrical surface of the downstream guide roller (11) and the downstream transport roller (15) being substantially tangent to a second plane (31) which is substantially parallel to the first plane, and a circumferential surface of both guide rollers (9, 11) or both transport rollers (13, 15) being substantially tangent to a third plane (33) which is located at a spaced apart location from the first plane (29) and the second plane (31) and which is parallel thereto,
• translational drive means (36, 71) connected to the sled (41) for periodically displacing the transport rollers (13, 15) generally perpendicular to the axes (25, 27) of the transport rollers, around an equilibrium position (39) located generally midway between the axes (19, 21) of the guide rollers (9, 11), the distance between the axes (25, 27) of the transport rollers (13, 15) being constant, and
• translation-balancing means (77) to maintain a generally constant position of a center of mass of the balancing means (77), the transport rollers (13, 15) and the sled (41).