Paper machine

• US 6,261,415 B1
• Filed: 08/26/1999
• Issued: 07/17/2001
• Est. Priority Date: 08/28/1998
• Status: Expired due to Fees

• Current Assignee: Valmet-Karlstad AB (Valmet Oyj)
• Original Assignee: Valmet-Karlstad AB (Valmet Oyj)
• Inventors: Johansson, Per Anders, Nyman, Mikael
• Primary Examiner(s): Chin, Peter
• Assistant Examiner(s): HALPERN, MARK
• Application Number:
  US09/383,809
• Time in Patent Office: 691 Days
• Field of Search: 162/191, 162/193, 162/194, 162/195, 162/198, 162/264, 162/286, 162/306, 162/358.1, 162/289, 162/DIG.10, 162/DIG.11, 162/202
• US Class Current: 162/193
• CPC Class Codes: D21F 7/04 Paper-break control devices
• CPC Class Codes: D21G 9/0063 Devices for threading a web tail through a paper-making machine
• CPC Class Codes: Y10S 162/10 Computer control of paper making variables
• CPC Class Codes: Y10S 162/11 Wet end paper making variables

Abstract

A paper machine and web control system for the same to be activated on web rupture, which paper machine has a double-felted press nip and a treatment unit for increasing the dry solids content of the web downstream of the press nip, the web being transferred from the press nip to the treatment unit in an open draw. The web control system has a water-application device arranged at the open draw to discharge jets of water against the upper press felt on rupture of the web so as to prevent an upstream end of the web continuing with the upper press felt, a felt-deflection device situated downstream of the press nip to bring the press felts into contact with each other downstream of the press nip on rupture of the web so as to sandwich the web between the felts, and a suction device in the loop of the lower press felt at a position between the press nip and the felt-deflection device to temporarily attach the web to the lower press felt by suction.

Claims

1. A paper machine for manufacturing a continuous paper web, comprising:

a wet section;

a press section including a double-felted press having a first press member and a second press member defining a nip therebetween, a first press felt arranged to travel in a loop through the press nip and around a first guide roll located downstream of the press nip, and a second press felt arranged to travel in a loop through the press nip and around a second guide roll located downstream of the press nip, the guide rolls being located in relation to each other such that the press felts normally diverge from each other after the press nip;

a treatment unit located downstream of the double-felted press for increasing the dry solids content of the web, wherein the web during normal operation traverses an open draw downstream of the press nip and upstream of the treatment unit; and

a web control system activatable upon a rupture of the web in said open draw so as to exert force on the web to prevent the web from adhering to and traveling with the first press felt beyond the first guide roll such that the web downstream of the first guide roll travels on the second press felt.

2. The paper machine of claim 1, further comprising a detector operable to detect a web rupture in said open draw, and a controller connected with the detector and with the web control system, the controller activating the web control system upon receipt of a signal from the detector indicating that a web rupture has occurred in said open draw.

3. The paper machine of claim 1, wherein the web control system comprises at least one of:

a water-application device arranged proximate said open draw and the first press felt and operable to discharge jets of water across and against the first press felt so as to prevent an upstream end of the web resulting from the web rupture from adhering to the first press felt;

a felt-deflection device disposed downstream of the press nip and operable to deflect one of the first and second press felts toward the other so as to bring the two press felts into contact with each other downstream of the press nip with the web sandwiched therebetween; and

a suction device arranged in the loop of the second press felt downstream of the press nip, the suction device being operable to apply suction through the second press felt upon a web rupture in said open draw so as to temporarily attach the web to the second press felt.

4. The paper machine of claim 3, wherein the web control system comprises the felt-deflection device and the suction device, the felt-deflection device and suction device being located relative to each other such that activation of the felt-deflection device causes the first and second press felts to be relatively moved toward each other to create a sandwich construction of the web between the two press felts, which sandwich construction is adjacent the suction device.

5. The paper machine of claim 4, wherein the felt-deflection device comprises a movable guide roll disposed within the loop of one of the press felts, the movable guide roll being movable so as to deflect said one of the press felts toward the other to create the sandwich construction.

6. The paper machine of claim 5, wherein the movable guide roll is disposed within the loop of the first press felt and the suction device is adjacent a surface of the second press felt that faces away from the movable guide roll.

7. The paper machine of claim 6, wherein the first guide roll for the first press felt is movable and forms the movable guide roll of the felt-deflection device.

8. The paper machine of claim 7, wherein the felt-deflection device includes an actuator coupled with the first guide roll for moving the first guide roll so as to create the sandwich construction.

9. The paper machine of claim 3, wherein the web control system comprises the water-application device, the felt-deflection device, and the suction device.

10. The paper machine of claim 3, wherein the web control system comprises the water-application device, and the water-application device includes nozzles oriented to discharge jets of water into said open draw for severing the web upon detection of an abnormal condition in the treatment unit.

11. The paper machine of claim 10, further comprising a detector arranged in the treatment unit for detecting an abnormal condition therein, and a controller coupled with the detector and with the water-application device for activating the water-application device to sever the web in the open draw upon receipt of a signal from the detector indicating occurrence of an abnormal condition in the treatment unit.

12. The paper machine of claim 10, wherein the water-application device is operable to cause the web to adhere to and travel with the second press felt downstream of the press nip.

13. The paper machine of claim 12, further comprising a reject-handling station downstream of the loop of the second press felt for receiving web material that is carried by the second press felt after the press nip.

14. The paper machine of claim 3, wherein the treatment unit includes a clothing arranged in a loop about a plurality of guide rolls and in contact with at least one treatment roll, and wherein a clothing-deflection device is arranged in the loop of said clothing and is operable to move the clothing into contact with the second press felt.

15. The paper machine of claim 14, wherein the web control system comprises the felt-deflection device in the form of a movable guide roll disposed within the loop of the first press felt, the movable guide roll being movable in concert with the clothing-deflection device to move the first press felt and the clothing into contact with the second press felt.

16. The paper machine of claim 3, wherein the web control system comprises the water-application device, the felt-deflection device, and the suction device, and further comprising a detector operable to detect a web rupture in said open draw, and a controller connected with the detector and with the web control system, the controller activating the web control system upon receipt of a signal from the detector indicating that a web rupture has occurred in said open draw.

17. A system for controlling a paper web in a paper machine upon rupture of the web along an open draw downstream of a press nip, the press nip being defined between first and second press members respectively disposed within loops of first and second press felts, the two press felts being guided by guide rolls so as to diverge from each other after the press nip, said system comprising:

a water-application device arranged proximate said open draw and the first press felt and operable to discharge jets of water across and against the first press felt so as to prevent an upstream end of the web resulting from the web rupture from adhering to and traveling with the first press felt downstream of the press nip;

a felt-deflection device disposed downstream of the press nip and operable to deflect one of the first and second press felts toward the other so as to bring the two press felts into contact with each other downstream of the press nip with the web sandwiched therebetween; and

a suction device arranged in the loop of the second press felt downstream of the press nip, the suction device being operable to apply suction through the second press felt upon a web rupture in said open draw so as to temporarily attach the web to the second press felt.

18. The system of claim 17, further comprising:

a detector proximate said open draw and operable to detect a rupture of the web in said open draw; and

a controller coupled with the detector and with the water-application device, the felt-deflecting device, and the suction device, the controller being operable to activate said devices upon receipt of a signal from the detector indicating that a rupture has occurred.

19. The system of claim 17 adapted for use in a paper machine having a treatment unit downstream of the press nip for increasing the dry solids content of the web, the treatment unit having a clothing traveling in a loop about a plurality of guide rolls and in contact with at least one treatment roll, the system further comprising a clothing-deflection device arranged in the loop of the clothing and operable to move the clothing into contact with the second press felt for facilitating threading a leading end of the web into the treatment unit.

20. A method for controlling a path of travel of a paper web in a paper machine upon rupture of the web along an open draw downstream of a press nip of the paper machine, the press nip being defined between first and second press members respectively disposed within loops of first and second press felts, the two press felts being guided by guide rolls so as to diverge from each other after the press nip and to separate from the web such that the web travels along said open draw during normal operation, said method comprising:

detecting a rupture of the web along said open draw;

directing one or more jets of fluid against and across the first press felt upon detection of the rupture so as to urge the web away from the first press felt and toward the second press felt; and

deflecting one of the press felts toward the other upon detection of the rupture so as to cause the press felts to come together with the web sandwiched therebetween.

21. The method of claim 20, further comprising applying suction through the second press felt upon detection of the rupture, the suction being applied in a region of the second press felt at which the web is sandwiched between the two press felts so as to urge the web against the second press felt.

22. The method of claim 20, wherein directing fluid jets comprises directing jets of water against the first press felt in a direction generally toward the second press felt.

23. The method of claim 20, further comprising:

detecting an abnormal condition in the paper machine downstream of the open draw; and

directing jets of fluid into the open draw upon detection of said abnormal condition so as to sever the web traveling over said open draw.