Patent EA-000942-B1 (EA)
Title: Method and drainage device for drainage of liquid from pulp or paper stock
Inventor: CABRERA Y LOPEZ CARAM LUIS FER
IPC: D21F1/48
Filed: 1997-02-11
Abstract: 1. A drainage device for use in a pulp or papermaking machine for drainage of liquid from pulp or paper stock contained on a fabric which passes over said device, comprising: a blade arrangement comprising a primary blade and a trail blade; a gap formed between the primary blade and a trail blade to allow drainage of liquid therethrough; said primary blade having a leading edge support surface adjacent the fabric for support thereof and a trailing surface that diverges downward from said support surface away from the fabric on the support surface so that a space is formed between said fabric and said trailing surface; said trail blade having a leading edge support surface for the fabric; means for maintaining controlled drainage from the paper stock by controlling flow of entrained liquid across the gap; said trailing surface of said primary blade being so formed with raised protuberances and valleys so as to force a portion of entrained liquid back through the fabric so as to create activity in the stock to enhance stock distribution. 2. The invention in accordance with claim 1 wherein said maintaining means is sizing of the width of the gap in the machine direction. 3. The invention in accordance with claim 2 wherein SAID drainage surface shape is designed tp force a portion of the liquid drained stock back through the fabric and paper stock while facilitating laminar flow in the machine direction. 4. The invention in accordance with claim 2 wherein said gap size is adjustable. 5. The invention in accordance with claim 1 wherein the space between the fabric and the drainage surface and the gap are filled with liquid during operation. 6. The invention in accordance with claim 2 wherein said device includes means for providing a controlled vacuum to said gap. 7. The invention in accordance with claim 6 wherein said controlled vacuum is provided by a suction box on which said drainage device is mounted. 8. The invention in accordance with claim 6 wherein said controlled vacuum is provided by a suction box on which said drainage device is mounted. 9. The invention in accordance with claim 5 wherein a plurality of drainage devices are mounted on respective suction boxes. 10. The invention in accordance with claim 3 wherein said drainage surface is formed having a plurality of curved surfaces. 11. The invention in accordance with claim 10 wherein said curves have a profile which shape is a function of speed of operation of a paper making machine. 12. The invention in accordance with claim 10 wherein said drainage surface diverges from said support surface at an angle of between 0 degree  and 10 degree . 13. The invention in accordance with claim 1 wherein said primary blade has two opposite ends and includes means preventing drained liquid from passing beyond said ends in a cross machine direction. 14. The invention in accordance with claim 13 wherein said preventing means includes providing a surface at each end which is flush with the fabric throughout the primary blade length in the machine direction. 15. The invention in accordance with claim 14 which includes deckle means located in the gap at the respective ends of the primary blade to prevent drained liquid from passing beyond said ends in a cross machine direction. 16. The invention in accordance with claim 1 which includes in combination therewith a mechanical device for inducing activity and disbursement of paper stock on a fabric. 17. The invention in accordance with claim 1 wherein said maintaining means is a self-adjusting hinged gate located in the gap. 18. A drainage device for use in a pulp or papermaking machine for drainage of liquid from pulp or paper stock contained on a fabric which passes over said device, comprising  a blade arrangement comprising a primary blade and a trail blade;  a gap formed between the primary blade and a trail blade to allow drainage of liquid therethrough; said primary blade having a leading edge support surface adjacent the fabric for support thereof and a trailing surface that diverges downward from said support surface away from the fabric on the support surface so that a space is formed between said fabric and said trailing surface; said trail blade having a leading edge support surface for the fabric;  means for maintaining said space and said gap filled with liquid by controlling flow of entrained liquid across the gap; and  said primary blade shape having raised protuberances and valleys which force some or all of the liquid drained back through the fabric to facilitate stock distribution and activity in the paper stock while facilitating laminar flow in the machine direction. 19. The invention in accordance with claim 18 wherein said maintaining means is the sizing of the width of the gap in the machine direction. 20. The invention in accordance with claim 19 wherein the drainage surface shape is defined by a series of curves in the drainage area which are so formed to minimize turbulence and create laminar flow. 21. The invention in accordance with claim 19 wherein said gap size is adjustable. 22. The invention in accordance with claim 18 wherein said maintaining means is a self-adjusting hinged gate located in the gap. 23. The invention in accordance with claim 19 wherein said device includes means for providing a controlled vacuum to said gap. 24. The invention in accordance with claim 23 wherein said controlled vacuum is provided by a suction box on which said drainage device is mounted. 25. The invention in accordance with claim 24 which includes a plurality of primary blades mounted on a common suction box. 26. The invention in accordance with claim 23 wherein a plurality of drainage devices are mounted on respective suction boxes. 27. The invention in accordance with claim 18 wherein said drainage surface is formed having a plurality of curved surfaces. 28. The invention in accordance with claim 27 wherein said curves have a profile which shape is a function of speed of operation of a paper making machine. 29. The invention in accordance with claim 27 wherein said drainage surface diverges from said support surface at an angle of between 0 degree  and 10 degree . 30. The invention in accordance with claim 18 wherein said primary blade has two opposite ends and includes means preventing drained liquid from passing beyond said ends in a cross machine direction. 31. The invention in accordance with claim 30 wherein said preventing means includes providing a surface at each end which is flush with the fabric throughout the primary blade length in the machine direction. 32. The invention in accordance with claim 30 which includes deckle means located in the gap at the respective ends of the primary blade to prevent drained liquid from passing beyond said ends in a cross machine direction. 33. The invention in accordance with claim 18 which includes in combination therewith a mechanical device for inducing activity and disbursement of paper stock on a fabric. 34. A drainage device for use in a pulp or papermaking machine for drainage of liquid from pulp or paper stock contained on a fabric which passes over said device, comprising  a blade arrangement comprising a primary blade and a trail blade;  a gap formed between the primary blade and a trail blade to allow drainage of liquid therethrough; said primary blade having a leading edge support surface adjacent the fabric for support thereof and a trailing surface that diverges downward from said support surface away from the fabric on the support surface so that between said fabric and said grainage surface a space is formed, said trail blade having a leading edge support surface for the fabric; means for maintaining said space and said gap filled with liquid, a primary blade is so configured that it inparts multiple pulses to the paper stock at a frequency and magnitude to reinforce CD shear. 35. The invention in accordance with claim 34 wherein said primary blade has several steps arranged in the machine direction so that to coincide with the points of natural inversion of CD shear. 36. The invention in accordance with claim 34 wherein said maintaining means is the sizing of the width of the gap in the machine direction. 37. The invention in accordance with claim 36 wherein said gap size is adjustable. 38. The invention in accordance with claim 35 wherein said maintaining means is a hinged gate located in the gap. 39. The invention in accordance with claim 36 wherein said device includes means for providing a controlled vacuum to said gap. 40. The invention in accordance with claim 39 wherein said controlled vacuum is provided by a suction box on which said drainage device is mounted. 41. The invention in accordance with claim 40 which includes a plurality of primary blades mounted on a common suction box. 42. The invention in accordance with claim 39 wherein a plurality of drainage devices are mounted on respective suction boxes. 43. The invention in accordance with claim 34 wherein said drainage surfaces are designed so as to allow a portion of the entrained liquid  to be forced back through the fabric. 44. The invention in accordance with claim 34 wherein said primary blade has two opposite ends and includes means preventing drained liquid from passing beyond said ends in a cross machine direction. 45. The invention in accordance with claim 44 wherein said preventing means includes providing a surface at each end which is flush with the fabric throughout the primary blade length in the machine direction. 46. The invention in accordance with claim 45 which includes deckle means located in the gap at the respective ends of the primary blade to prevent drained liquid from passing beyond said ends in a cross machine direction. 47. The invention in accordance with claim 34 which includes in combination therewith a mechanical device for inducing activity and disbursement of paper stock on a fabric. 48. The invention in accordance with claim 34 wherein said mai