SYSTEMS AND METHODS FOR PROVIDING RAPID AND SAFE OPENING OF PRESSURE NIP ROLLS

An actuator system for maintaining high nip forces at a roller nip is disclosed. The actuator system includes a primary actuator for urging a roller into an engaged position at which the roller contributes to providing the high nip forces at the roller nip, the primary actuator being provided attached to a movable mounting structure, and a secondary actuator for maintaining the mounting structure in a locked position, and for releasing the mounting structure, and therefore the primary actuator, from the locked position in the event of a power loss to the secondary actuator.

FIELD OF THE INVENTION

The present invention generally relates to the field of controls systems for pressure nip rolls, and relates in particular to safety systems for use in such control systems.

BACKGROUND

Mechanical actuators are commonly used in applications where high nip forces are needed in the production, for example, of polymer film and sheet. These actuators generally require either electric or hydraulic power to exercise position and gap control of one or more of the nip rollers. In the event of an emergency (such as loss of power), safety to personnel is a significant concern. If power is lost, the nip rollers may bind, lock up or respond in an unpredictable way.

Further, any material that is moving through the nip may continue moving in an uncontrolled fashion, endangering personnel. It is also possible that the nip rollers themselves and other equipment may become damaged from such an emergency, let alone the material being processed by the pressure nip rollers.

The remains a need therefore, for an improved safety system for pressure nip rollers.

SUMMARY

In accordance with an embodiment, the invention provides an actuator system for maintaining high nip forces at a roller nip. The actuator system includes a primary actuator for urging a roller into an engaged position at which the roller contributes to providing the high nip forces at the roller nip, the primary actuator being provided attached to a movable mounting structure, and a secondary actuator for maintaining the mounting structure in a locked position, and for releasing the mounting structure, and therefore the primary actuator, from the locked position in the event of a power loss to the secondary actuator.

In accordance with another embodiment, the invention provides an actuator system for maintaining high nip forces at a roller nip. The actuator system includes a primary actuator system for urging a roller into an engaged position at which the roller contributes to providing the high nip forces at the roller nip, the primary actuator system including at least one primary actuator that is provided attached to a base, and a secondary actuator system for maintaining the base in a locked position, and for releasing the mounting structure, and therefore the primary actuator system, from the locked position in the event of a power loss to the secondary actuator system.

In accordance with a further embodiment, the invention provides a method of maintaining high nip forces at a roller nip. The method comprising the steps of urging a roller into an engaged position at which the roller contributes to providing the high nip forces at the roller nip, and releasing a mounting structure to thereby release the roller from the roller nip in the event of a power loss to the secondary actuator.

The drawings are shown for illustrative purposes only.

DETAILED DESCRIPTION

In accordance with an embodiment, the invention provides an actuator system for maintaining high nip forces at a roller nip. The actuator system includes a primary actuator and a secondary actuator. The primary actuator is for urging a roller into an engaged position at which the roller contributes to providing the high nip forces at the roller nip. The primary actuator is provided attached to a movable mounting structure. The secondary actuator is for maintaining the mounting structure in a locked position, and for releasing the mounting structure, and therefore the primary actuator, from the locked position in the event of a power loss to the secondary actuator. In certain embodiments, the mounting structure includes a primary actuator base, the primary actuator includes a high force mechanical actuator and the secondary actuator includes a pneumatic cylinder.

FIG. 1, for example, diagrammatically shows a system10in accordance with an embodiment of the present invention that includes a pair of primary actuators12, such as high force mechanical actuators (e.g., jack screws13), for urging a roller14toward another roller16to form a roller nip under high pressure. The primary actuator12may include a mounting structure20on a system base22, and may be engaged to urge the roller14toward the roller16by way of the pair of mechanical actuators13.

FIG. 2Ashows the roller14not yet urged into engagement with the roller16, andFIG. 2Bshows the primary actuator urging the roller14into the engaged position against the roller16. The roller14slides on a fixed base18. The primary actuator20is also slidably mounted on the base22, and the primary actuator20is actively held in position by a secondary actuator system24. The secondary actuator system24includes a linkage system28that includes link members32,34that are pivotally coupled to each other and to both a rod25(that is coupled to the primary actuator12) and to a piston30of a pneumatic cylinder26that is maintained in a power-on state as shown at27inFIGS. 2A and 2B.

The primary actuator12may be an actuator that is not affected by a loss of power, and may be mounted on the mounting structure20, such as a primary actuator base. The primary actuator base20may be slidable on the system base22, and may be held in a locked position by a secondary actuator24, including the pneumatic cylinder26and the linkage system28. The rollers14,16may be any arbitrary length, and the system10may include the above components at each of the two ends of the roller14, for urging the roller14into contact with the roller16by pushing the ends of the roller14toward the roller16. In various embodiments, bases18and22may be separate bases or may be combined as a single based (as shown inFIG. 6), and may be fixed to a floor or may be movable.

FIG. 2Cshows the system10wherein the secondary actuator24(and possibly the entire system) loses power. Upon a power loss, the pneumatic cylinder26would release its piston30from being held in the extended position (shown inFIGS. 2A and 2B). The piston30is released back into the cylinder26(and thereby shortens), which permits the “L” shaped linkage member32of the linkage system28to swing downward, permitting a first end of a link34of the linkage system28to also be lowered with the member32. The first end of the link34is coupled to the member32, and a second end of the link34is coupled to the rod25. When the piston30is released upon loss of power to the pneumatic cylinder, the action of the linkage system28draws the mounting structure20toward the secondary actuator24, thereby moving the primary actuator and the roller14away from the roller16.

FIGS. 3A and 4Ashow the primary actuator being actively held in position by the cylinder26of the secondary actuator system24.FIGS. 3B and 4Bshow the secondary actuator system24upon a loss of power to the secondary actuator system24. As shown, the cylinder26withdraws the piston30(upon power loss), and the linkage system28swings down to draw the rod25(and therefore the primary actuator12and the cylinder14) away from the cylinder16.

FIGS. 5A and 5Bshow top views of the system ofFIG. 1with the primary actuator being actively held in position by the cylinder26of the secondary actuator system24(FIG. 5A), and show the secondary actuator system24upon a loss of power to the secondary actuator system24(FIG. 5B).

In accordance with another embodiment, a system50may include a pair of primary actuators52, such as high force mechanical actuators (e.g., jack screws53), for urging a roller54toward another roller56to form a roller nip under high pressure. The primary actuator12may include a mounting structure60on a unitary system base58, and may be engaged to urge the roller54toward the roller56by way of the pair of mechanical actuators53.

The system includes a linkage system similar to the above embodiment, and while the secondary actuator system64is activated in the locked position, a pneumatic cylinder66, via a linkage system, locks the base52of the primary actuator system such that the roller54is urged against the roller56. When power to the pneumatic cylinder66is shut off (e.g., in an emergency power outage), the piston of the pneumatic cylinder66retracts, causing the linkage system to relax and draw the base52of the primary actuator system away from the roller56as discussed above.FIG. 6shows that the primary actuator system52may include a pair of primary actuators, one at either end of the roller length, and the secondary actuator system64may also include a pair of secondary actuators, one at either end of the roller length, and that work with a base of each primary actuator as discussed above.

The system therefore provides an actuator system for maintaining high nip forces at a roller nip, and includes a primary actuator system and a secondary actuator system. The actuator system includes the primary actuator system for urging a roller into an engaged position at which the roller contributes to providing the high nip forces at the roller nip. The primary actuator system includes at least one primary actuator that is provided attached to a base. The secondary actuator system is for maintaining the base in a locked position, and for releasing the mounting structure, and therefore the primary actuator system, from the locked position in the event of a power loss to the secondary actuator system.