RAPID AND SAFE OPENING

OF PRESSURE NIP ROLLS

PRIORITY

The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/502,954 filed May 8, 2017, the disclosure of which is hereby incorporated by reference in its entirety.

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. BRIEF DESCRIPTION OF THE DRAWINGS

The following description may be further understood with reference to the accompanying drawings in which:

Figure 1 shows an illustrative diagrammatic isometric view of a system in accordance with an embodiment of the present invention;

Figures 2A - 2C show illustrative diagrammatic side views of the system of Figure 1 with the nip rolls not engaged (Figure 2A), with the nip rolls engaged (Figure 2B), and with a locking actuator released in the event of a power loss;

Figures 3 A and 3B show illustrative diagrammatic isometric front views of a portion of the system of Figure 1 with the locking actuator engaged (Figure 3A) and released (Figure 3B);

Figures 4 A and 4B show illustrative diagrammatic isometric rear views of a portion of the system of Figure 1 with the locking actuator engaged (Figure 4A) and released (Figure 4B);

Figures 5 A and 5B show illustrative diagrammatic isometric top views of the system of Figure 1 with the locking actuator engaged (Figure 5A) and released (Figure 5B); and

Figure 6 shows an illustrative diagrammatic isometric view of a system in accordance with another embodiment of the present invention that includes a pair of unitary bases.

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.

Figure 1 , for example, diagrammatically shows a system 10 in accordance with an embodiment of the present invention that includes a pair of primary actuators 12, such as high force mechanical actuators (e.g., jack screws 13), for urging a roller 14 toward another roller 16 to form a roller nip under high pressure. The primary actuator 12 may include a mounting structure 20 on a system base 22, and may be engaged to urge the roller 14 toward the roller 16 by way of the pair of mechanical actuators 13,

Figure 2A shows the roller 14 not yet urged into engagement with the roller 16, and Figure 2B shows the primary actuator urging the roller 14 into the engaged position against the roller 16. The roller 14 slides on a fixed base 18. The primary actuator 20 is also slidably mounted on the base 22, and the primary actuator 20 is actively held in position by a secondary actuator system 24. The secondary actuator system 24 includes a linkage system 28 that includes link members 32, 34 that are pivotally coupled to each other and to both a rod 25 (that is coupled to the primary actuator 12) and to a piston 30 of a pneumatic cylinder 26 that is maintained in a power-on state as shown at 27 in Figures 2 A and 2B.

The primary actuator 12 may be an actuator that is not affected by a loss of power, and may be mounted on the mounting structure 20, such as a primary actuator base. The primary actuator base 20 may be slidable on the system base 22, and may be held in a locked position by a secondary actuator 24, including the pneumatic cylinder 26 and the linkage system 28. The rollers 14, 16 may be any arbitrary length, and the system 10 may include the above components at each of the two ends of the roller 14, for urging the roller 14 into contact with the roller 16 by pushing the ends of the roller 14 toward the roller 16. In various embodiments, bases 18 and 22 may be separate bases or may be combined as a single based (as shown in Figure 6), and may be fixed to a floor or may be movable.

Figure 2C shows the system 10 wherein the secondary actuator 24 (and possibly the entire system) loses power. Upon a power loss, the pneumatic cylinder 26 would release its piston 30 from being held in the extended position (shown in Figures 2 A and 2B). The piston 30 is released back into the cylinder 26 (and thereby shortens), which permits the "L" shaped linkage member 32 of the linkage system 28 to swing downward, permitting a first end of a link 34 of the linkage system 28 to also be lowered with the member 32. The first end of the link 34 is coupled to the member 32, and a second end of the link 34 is coupled to the rod 25. When the piston 30 is released upon loss of power to the pneumatic cylinder, the action of the linkage system 28 draws the mounting structure 20 toward the secondary actuator 24, thereby moving the primary actuator and the roller 14 away from the roller 16.

Figures 3 A and 4 A show the primary actuator being actively held in position by the cylinder 26 of the secondary actuator system 24. Figures 3B and 4B show the secondary actuator system 24 upon a loss of power to the secondary actuator system 24. As shown, the cylinder 26 withdraws the piston 30 (upon power loss), and the linkage system 28 swings down to draw the rod 25 (and therefore the primary actuator 12 and the cylinder 14) away from the cylinder 16.

Figures 5 A and 5B show top views of the system of Figure 1 with the primary actuator being actively held in position by the cylinder 26 of the secondary actuator system 24 (Figure 5 A), and show the secondary actuator system 24 upon a loss of power to the secondary actuator system 24 (Figure 5B).

In accordance with another embodiment, a system 50 may include a pair of primary actuators 52, such as high force mechanical actuators (e.g., jack screws 53), for urging a roller 54 toward another roller 56 to form a roller nip under high pressure. The primary actuator 12 may include a mounting structure 60 on a unitary system base 58, and may be engaged to urge the roller 54 toward the roller 56 by way of the pair of mechanical actuators 53.

The system includes a linkage system similar to the above embodiment, and while the secondary actuator system 64 is activated in the locked position, a pneumatic cylinder 66, via a linkage system, locks the base 52 of the primary actuator system such that the roller 54 is urged against the roller 56. When power to the pneumatic cylinder 66 is shut off (e.g., in an emergency power outage), the piston of the pneumatic cylinder 66 retracts, causing the linkage system to relax and draw the base 52 of the primary actuator system away from the roller 56 as discussed above. Figure 6 shows that the primary actuator system 52 may include a pair of primary actuators, one at either end of the roller length, and the secondary actuator system 64 may 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.

Those skilled in the art will appreciate that numerous modifications and variations may be made to the above disclosed embodiments without departing from the spirit and scope of the present invention.