Variable frequency dewatering assembly Number:6,802,940 from the United States Patent and Trademark Office (PTO) owispatent A variable frequency foil (VFF) box assembly and mechanisms for moving individual foils/foil beams and individual foil beam sets relative to each other to adjust the frequency of a paper making machine, and method of use are provided. The VFF box assembly allows for continuously and uniformly adjusting the pitch distances of individual foils within foil sets over a finite range, and also adjusting the distance between foil sets during the continuous operation of a paper making machine. Also provided is a variable frequency assembly comprising a combination of dewatering elements such as one or more foil elements and table rolls, a multi-surfaced foil element, and/or an adjustable angle foil element.<H dewatering, frequency, Variable, freque, 6802940.html, Patent, pto, 6802940

Title: Variable frequency dewatering assembly

Abstract: A variable frequency foil (VFF) box assembly and mechanisms for moving individual foils/foil beams and individual foil beam sets relative to each other to adjust the frequency of a paper making machine, and method of use are provided. The VFF box assembly allows for continuously and uniformly adjusting the pitch distances of individual foils within foil sets over a finite range, and also adjusting the distance between foil sets during the continuous operation of a paper making machine. Also provided is a variable frequency assembly comprising a combination of dewatering elements such as one or more foil elements and table rolls, a multi-surfaced foil element, and/or an adjustable angle foil element.

Patent Number: 6,802,940 Issued on 10/12/2004 to Frawley, et al.

Inventors: Frawley; Thomas E. (Appleton, WI); VanRens; Mark R. (DePere, WI); Theut; Patrick J. (Tomahawk, WI); Wouters; Alan (Appleton, WI)
Assignee: Appleton International, Inc. (Kimberly, WI)

Appl. No.: 10/281,688

Filed: October 28, 2002

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
972144	Oct., 2001	6471829

Current U.S. Class: 162/352 ; 162/208; 162/211; 162/354; 162/374

Current International Class: D21F 1/48 (20060101)

Field of Search: 162/208,209,211,351-356,374

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Primary Examiner: Chin; Peter
Assistant Examiner: Hug; Eric
Attorney, Agent or Firm: Whyte Hirschboeck Dudek SC

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 09/972,144 (Publ. No. US2002/0067544), filed Oct. 5, 2001, now U.S. Pat. No. 6,471,829, and claims the benefit of U.S. Provisional Application Ser. No. 60/238,930, filed Oct. 10, 2000.

Claims

What is claimed is:

1. An assembly for dewatering in a papermaking apparatus, comprising: first and second sets of dewatering elements, the dewatering elements of at least one set comprising at least one foil beam and at least one table roll; and an actuating mechanism operable to laterally move and space apart the dewatering elements by a standard interval, and to laterally move at least one of the sets to space apart the sets by an integer multiple of the standard interval.

2. The assembly according to claim 1, wherein the dewatering elements are mounted in a support comprising a box shaped frame.

3. The assembly according to claim 1, wherein the dewatering elements are mounted on a support structure comprising rails.

4. An assembly for a papermaking apparatus, comprising: two or more sets of dewatering elements, the dewatering elements of at least one set comprising at least one foil beam at least and one table roll; and an actuating mechanism operable to laterally move the dewatering elements relative to each other to provide a pitch distance X between each dewatering element, and to provide a distance that is an integer multiple of the pitch distance X between a dewatering element of a first set and an adjacent dewatering element of a second set.

5. An assembly for a papermaking apparatus, comprising: at least first and second sets of dewatering elements, each set comprising at least two dewatering elements mounted on a support, and an actuating mechanism connecting the at least two dewatering elements and the sets of dewatering elements, the actuating mechanism operable to alter pitch distance between the dewatering elements whereby the dewatering elements of a set are substantially equidistant relative to each other, and adjacent sets of dewatering elements are spaced apart at an integer multiple of the distance between the dewatering elements.

6. The assembly of claim 5, wherein the dewatering elements of the first set comprises at least one foil beam and at least one table roll.

7. An assembly for a papermaking apparatus, comprising: at least first and second sets of dewatering elements, each set comprising at least a first and second dewatering element mounted on a support, and an actuating mechanism connecting at least one of the dewatering elements of each of the sets of dewatering elements, the actuating mechanism operable to laterally move said dewatering elements and space apart the dewatering elements of a set by a standard interval, and to laterally move a dewatering element of at least one of the sets of dewatering elements to space apart the sets by an integer multiple of the standard interval.

8. The dewatering assembly of claim 7, wherein the first set of dewatering elements comprises one or more foil beams and one or more table rolls.

9. The assembly according to claim 7, wherein each of the sets comprises a leading and a trailing dewatering element; and the actuating mechanism is connected to the leading dewatering elements of the first and second sets, and is operable to move the leading dewatering element of the second set relative to the trailing dewatering element of the first set to alter a distance between the sets.

10. The assembly according to claim 7, wherein each of the sets comprises a leading and a trailing dewatering element; and an actuator operable to laterally move the trailing dewatering element relative to the leading dewatering element.

11. The assembly according to claim 7, wherein the dewatering elements are mounted on a support comprising rails.

12. The assembly according to claim 11, wherein the support comprises an inner pair of rails and an outer pair of rails, and the first dewatering element is mounted on one of the pair of rails and the second dewatering element is mounted on the other of the pair of rails.

13. The assembly according to claim 12, wherein the first dewatering element of the first set is affixed to the rails in a stationary position, and the first dewatering element of the second set and the second dewatering elements of the first and second sets are slidably mounted on the rails.

14. The assembly according to claim 7, wherein the actuating mechanism comprises: a mating screw and nut assembly in rotatable contact with a gear mounted on a shaft, and rotating the shaft causes said lateral movement of the dewatering elements, the sets, or both.

15. The assembly according to claim 7, wherein the actuating mechanism comprises a hydraulic or pneumatic device.

16. The assembly according to claim 7, further comprising at least one linear bearing supported by a shaft, the linear bearing attached to at least one dewatering element and oriented perpendicular to the dewatering elements to maintain lateral alignment of the dewatering elements relative to each other.

17. The assembly according to claim 7, wherein the actuating mechanism comprises a hydraulic or pneumatic cylinder attached on at least one of the dewatering elements and comprising a mechanism for communicating the position of the attached element to a controller and receiving a signal from the controller to actuate the cylinder to laterally move the attached element to alter the pitch distance between the attached element and another element.

18. The assembly according to claim 7, wherein the actuating mechanism comprises a first actuating screw and nut assembly affixed to one of the dewatering elements and oriented perpendicular to the dewatering elements, the actuating screw connected to an actuating device operable to move the actuating screw to laterally move the affixed element to alter the pitch distance between the affixed element and another element.

19. The assembly according to claim 18, wherein the actuating device comprises a worm/gear assembly mounted on a drive shaft.

20. The assembly according to claim 7, wherein the actuating mechanism comprises a pantograph assembly connecting the dewatering elements.

21. The assembly according to claim 7, wherein the actuating mechanism comprises a telescoping shaft assembly.

22. The assembly according to claim 7, wherein the actuating mechanism comprises a rack gear engaged with a pinion gear.

23. An assembly for a papermaking apparatus, comprising: first and second sets of dewatering elements, each set comprising at least two dewatering elements supported on a rail system, the dewatering elements of at least one set comprising at least one foil beam and at least one table roll; and a mechanism operable to move at least one dewatering element of the first set to alter a pitch distance between two dewatering elements of the first set by a distance X, and to move a dewatering element of the second set relative to the first set to alter an interset distance between the first and second sets by an integer multiple of distance X.

24. The assembly according to claim 23, wherein the rail system is affixed to a frame of a paper making machine.

25. The assembly according to claim 23, wherein the mechanism is operable to move a dewatering element of the second set by a distance X from a second dewatering element of the second set.

26. In an apparatus comprising a two or more sets of dewatering elements, each set comprising a plurality of dewatering elements mounted on a support, a mechanism to alter the pitch distance between individual dewatering elements of the sets whereby the individual dewatering elements are maintained at a distance X relative to each other, and to alter the distance between adjacent sets to maintain the distance as an integer multiple of the distance X of the dewatering elements.

27. In a dewatering assembly comprising a two or more sets of dewatering elements with each set comprising a plurality of dewatering elements each being mounted on a support, a mechanism for adjusting the frequency of the assembly, the mechanism connected to the dewatering elements and operating to alter pitch distance between individual dewatering elements of the set to maintain the elements at substantially equal spacing relative to each other, and connected to the sets and operating to alter the distance between the sets to an interset distance as an integer multiple of the spacing of the elements.

28. A foil beam assembly, comprising: at least a first and a second foil beam set, each foil beam set comprising a plurality of foil beams; and an actuating mechanism operable to laterally move the foil beams to space apart the foil beams by a standard interval, and to laterally move at least one of the foil beam sets to space apart the foil beam sets by an integer multiple of the standard interval.

29. The foil beam assembly according to claim 28, wherein the foil beam sets have a combined frequency adjustable by the lateral movement of the foil beams by the actuating mechanism.

30. The foil beam assembly according to claim 28, wherein the foil beam sets have a combined frequency adjustable by the lateral movement of the at least one foil beam set by the actuating mechanism.

31. The foil beam assembly according to claim 28, wherein at least one of the foil beam sets comprises at least one table roll, and the actuating mechanism is operable to space apart the table roll relative to a foil beam by a standard interval.

32. A foil assembly, comprising: at least a first and a second foil set, each foil set comprising a plurality of foil elements; and an actuating mechanism operable to laterally move the foil elements to space apart the foil elements by a standard interval, and to laterally move at least one of the foil elements sets to space apart the foil sets by an integer multiple of the standard interval.

33. The foil assembly of claim 32, wherein the foil elements comprise at least one foil element comprising a unitary structure comprising two wire-contacting surfaces spaced apart by the standard interval with a suction-forming section and a drainage section therebetween.

34. The foil assembly of claim 32, wherein the foil elements comprise at least one foil element comprising a unitary structure comprising: a suction-forming section comprising a leading edge, a wire contacting surface, and a suction-producing surface; a trailing section comprising a leading edge and a wire contacting surface; and a water drainage slot disposed between the suction-producing surface and the leading edge of the trailing section.

35. A foil assembly, comprising: at least a first and a second foil set, each foil set comprising a plurality of foil elements, at least one foil element comprising a unitary structure comprising two wire-contacting surfaces spaced apart by a standard interval with a drainage section therebetween; and an actuating mechanism operable to laterally move the foil elements to space apart the foil elements by the standard interval, and to laterally move at least one of the foil sets to space apart the foil sets by an integer multiple of the standard interval.

36. The foil assembly of claim 35, wherein the at least one foil element comprises: a suction-forming section comprising a leading edge, a wire contacting surface, and a suction-producing surface; and a trailing section comprising a leading edge and a wire contacting surface.

37. The foil assembly of claim 35, wherein the drainage section comprises a drainage slot disposed between the suction-producing surface of the suction-forming section and the leading edge of the trailing section.

38. An assembly for dewatering in a papermaking apparatus, comprising: at least a first and a second set of dewatering elements, each set comprising at least one foil element comprising a unitary structure comprising two wire-contacting surfaces spaced apart by a standard interval with a drainage section therebetween; and an actuating mechanism operable to laterally move the dewatering elements to space apart the dewatering elements by the standard interval, and to laterally move at least one of the sets to space apart the sets by an integer multiple of the standard interval.

39. The assembly of claim 38, wherein the at least one foil element comprises: a suction-forming section comprising a leading edge, a wire contacting surface, and a suction-producing surface; and a trailing section comprising a leading edge and a wire contacting surface; and the drainage section comprises a drainage slot disposed between the suction-producing surface of the suction-forming section and the leading edge of the trailing section.

40. The assembly of claim 38, wherein at least one set comprises one or more table rolls.

41. The assembly of claim 38, wherein at least one set comprises a foil beam having a single wire contacting surface.

42. An assembly for dewatering in a papermaking apparatus, comprising: at least first and second sets of dewatering elements, at least one set comprising at least one adjustable angle foil; and an actuating mechanism operable to laterally move the dewatering elements to space apart the dewatering elements by a standard interval, and to laterally move at least one of the dewatering elements sets to space apart the sets by an integer multiple of the standard interval.

43. A method of varying the frequency of a dewatering assembly, comprising the steps of: providing the dewatering assembly comprising a plurality of dewatering elements, the dewatering elements comprising at least two sets of dewatering elements; and an actuating mechanism operable to laterally move said dewatering elements; and actuating the actuating mechanism to move the dewatering elements to alter a distance between the dewatering elements and space apart the dewatering elements within a set at about a distance X and adjacently situated dewatering elements of adjacent sets at about the distance X or an integer multiple of the distance X of about 2X or greater.

44. A dewatering assembly, comprising: at least two sets of dewatering elements, each set comprising at least two dewatering elements; and an actuating mechanism operable to move said dewatering elements during a continuous operation of a papermaking apparatus and position the dewatering elements of a set at an about equidistant spacing and adjacent dewatering elements of adjacent sets at about said equidistant spacing or an integer multiple of said equidistant spacing of about 2X or greater.

45. A dewatering assembly, comprising: a plurality of dewatering elements, the dewatering elements comprising at least two sets of dewatering elements; at least one of the dewatering elements of each set being connected an actuating mechanism, the actuating mechanism being operable to move the dewatering elements connected thereto and to space apart the dewatering elements of a set at a distance of standard interval, and to space apart adjacently situated dewatering elements of adjacent sets at a distance of about the standard interval X or an integer multiple of the standard in several of about 2X or greater.

46. The dewatering assembly of claim 45, wherein a first set of dewatering elements comprises one or more foil beams and one or more table rolls.

47. The dewatering assembly of claim 45, wherein the dewatering elements comprise foil beams.

48. A dewatering assembly, comprising: at least two sets of dewatering elements, each set comprising at least two dewatering elements; and an actuating mechanism operable to move said dewatering elements; wherein a distance between two adjacent dewatering elements within a set is at a standard interval, and a distance between two other adjacent dewatering elements within said set is at an integer multiple of the standard interval of about 2X or greater, and a distance between adjacent dewatering elements of adjacent sets is at the standard interval or an integer multiple of the standard interval of about 2X or greater.

49. A dewatering assembly, comprising: a plurality of dewatering elements, at least one dewatering element being stationary and other of the dewatering elements being moveable relative to each other and to the stationary dewatering element, the moveable dewatering elements comprising at least two sets of dewatering elements; and an actuating mechanism operable to move the movable dewatering elements to alter distance be wean the dewatering elements and maintain the dewatering elements within a set at about a standard interval X, and to vary the distance between adjacently situated dewatering elements of adjacent sets at about the standard interval or an integer multiple of the standard interval of out 2X or greater.

50. In a papermaking apparatus comprising a dewatering assembly, the assembly comprising a plurality of dewatering elements, the dewatering elements comprising at least two sets of dewatering elements; a mechanism operable to alter a distance between the dewatering elements and to space apart the dewatering elements within a set at a distance of about a standard interval and to space apart adjacently situated dewatering elements of adjacent sets at about the standard interval or an integer multiple of the standard interval of about 2X or greater.

51. A dewatering assembly, comprising: a plurality of dewatering elements, the dewatering elements comprising at least two sets of dewatering elements; an actuating mechanism operable to move said dewatering elements and position the dewatering elements of a set at an about equidistant spacing and adjacently situated dewatering elements of adjacent sets at about said equidistant spacing or an integer multiple of said equidistant spacing of about 2X or greater, and a mechanism for indicating the position of the dewatering elements relative to each other.

52. The assembly of claim 51, wherein the mechanism is mounted on one or more of the dewatering elements.

53. The assembly of claim 51, wherein the mechanism comprises a position feedback transducer.

54. The assembly of claim 51, wherein the mechanism is integral to the actuating mechanism.

55. The assembly of claim 51, wherein the mechanism is operable to communicate with a controller and receive a signal from the controller whereby the actuating mechanism is actuated to move the dewatering elements.

Description

FIELD OF THE INVENTION

The present invention relates to an apparatus and system for altering the frequency of a Fourdrinier table in the formation of a continuous web of paper or other material.

BACKGROUND OF THE INVENTION

In the manufacture of paper, a stock of fibers and mineral fillers suspended in water, is deposited onto the moving wire on the Fourdrinier table of a paper machine. An example of a conventional Fourdrinier table assembly 10 is shown in FIG. 1. The table 10 includes a head box 12 from which a stock suspension is deposited onto a continuously moving wire 14, a breast roll 16, forming unit 18, and a series of gravity foil boxes 20 and vacuum foil boxes 22, a dandy roll 24, a series of suction boxes 26, and a couch roll 28. As the stock suspension moves along the wire 14 and over the foil boxes 20, 22 and suction boxes 26, the water is removed to form a continuous web.

Many theories have been applied to enhance water removal and achieve proper fiber orientation and distribution to form the fiber sheet, but with varying degrees of success. In one practice, table rolls have been used to apply a vacuum pulse by drawing water from the undersurface of the wire, and then create a pressure pulse by pushing water through the fabric to agitate the stock suspension for proper fiber orientation. However, as production speeds increased and higher vacuum forces were applied, excessive jumping of the stock of the forming sheet occurred which adversely affected formation quality. With the development of hydrofoils, control of water removal and formation improved.

From 1960 to 1970, machines became faster and wider, and the gravity foil box was introduced. The device consisted of a bridge-like framework that spanned the table with "T" bars installed for the individual blades. Foil blades could be removed or added on the run, and the spacing of the "foil banks" was random at best. The concept of foil angle was then proposed and experimentation was performed to determine optimal foil blade angle and foil bank spacing on the machine, which are important to drainage and formation.

A subsequent development was the concept of table harmonics, an engineering principle stating that the energy contained within the stock at the exit of the head box can be amplified (for improved drainage and formation) by the spacing of the foils. The harmonic excitation of the stock can be further altered by placing foil banks at specific intervals along the table based on the tip-to-tip spacing of the foils within each bank. This principle gave rise to the practice of placing the start of a first foil bank in the vicinity of three to six feet from the exit of the head box. It was also learned that the ability to add or remove foils from a bank significantly impacted sheet properties. However, foil banks could not be moved while the machine was running due to the tremendous drag imparted onto the foils. In about 1978, the concept of table frequency was combined with table harmonics to maximize drainage and formation. It was discovered that packing a table with foils spaced an appropriate distance apart, and then removing the foils from the table in strategic locations, achieved the desired Fourdrinier frequency when operating at higher speeds, up to 3300 fpm and higher.

Another development included the introduction of an automated foil bank that varied the pitch of the foil blade (the variable angle foil) to impact drainage and formation. It was also determined that the best formation and drainage for any given table was a frequency between 55 Hz and 105 Hz. In addition, a foil bank system was introduced that could raise foils into the wire and/or drop them from contact with the wire, but only allowed the use of a finite number of frequencies (i.e., either 55 or 75 Hz) by the papermaker. This limits the success of the papermaker where another frequency (i.e., 61 Hz) would be optimal for formation and drainage.

The function of the Fourdrinier table is two-fold: (1) to de-water the stock utilizing the effects of both gravity and applied vacuum, and (2) to subject the stock to periodic excitation as the wire passes over a series of inverted continuous hydrofoil blades (foils) that extend transversely across the table in a cross machine direction, i.e., at a right angle to the direction in which the wire travels.

Traditionally, a Fourdrinier table include several sections of foil groupings, or sets, of approximately six foils each, that are mounted on individual foil support beam structures (i.e., T-bar mounts spaced along the length of the table at set intervals to create a desired pulse frequency. The foil sets are normally affixed to a sub-structure of the table commonly referred to as a "box." An example of a conventional foil box 32 having four foils 34 is shown in FIG. 2. The direction of the movement of the wire (not shown) over the foils 34 is shown by arrow 30. The boxes are further sub-classified into either gravity boxes 20 or vacuum boxes 22 (FIG. 1). The first several foil sets aid in de-watering the stock under the influence of gravity. Further down the table as the water content of the stock decreases, a vacuum is applied from beneath the wire to facilitate the de-watering process.

The foils aid in the de-watering process and also impart a pressure impulse to the stock suspension. The impulses serve to keep the fibers and fillers in suspension during the de-watering process yielding a paper stock of uniform consistency. A single pulse is not adequate to control the stock on the Fourdrinier table. Rather, a series of pulses is generated and repeated at a standard interval.

The frequency of these impulses is referred to as the Fourdrinier frequency, which is defined as the velocity of the wire (in inches-per-second) divided by the pitch distance between the foils (in inches). It is well known to those versed in the art/science of papermaking that the frequency of these impulses has a dramatic effect upon the formation of the paper fibers. Under most circumstances, acceptable formation occurs at a Fourdrinier frequency between about 55 hertz and about 90 hertz. However, the current state of the art/science of paper formation relies upon the strategic use of conventional foil blades, multi-pulse foils, and/or foil boards that compromise effective stock de-watering with appropriate stock excitation frequencies.

SUMMARY OF THE INVENTION

The present invention provides variable frequency foil (VFF) box assemblies and mechanisms for moving individual foils/foil beams and individual foil beam sets relative to each other to adjust the frequency of a paper making machine independent of the wire speed. The invention allows for continuously and uniformly adjusting the pitch distances of individual foils within foil sets over a finite range, and also adjusting the distance between foil sets during the operation of a paper making machine. The invention also provides variable frequency dewatering assemblies that comprise various dewatering elements such as a foil beam and table roll in combination, and assemblies that incorporate multi-surface foil elements and adjustable angle foil blades.

In one aspect, the invention provides a foil beam assembly. In one embodiment, the foil beam assembly comprises at least a first and a second foil beam set, each foil beam set comprising a leading foil beam, a trailing foil beam, and at least one intermediate foil beam disposed therebetween, and a mechanism to laterally move the foil beams and the foil sets relative to each other. The mechanism is connected to each of the foil beams and to the first and second foil beam set. The mechanism is operable to laterally move the foil beams to alter the pitch distance such that each of the foil beams are spaced apart by a standard interval, and to laterally move at least one of the foil beam sets to alter the distance therebetween such that the foil beam sets are spaced apart by an integer multiple of the standard interval.

In one embodiment of the foil beam assembly, the mechanism can comprise a mating screw and nut assembly affixed to a first foil beam and an adjacent second foil beam, and in rotatable contact with a gear mounted on a shaft, whereby rotating the shaft causes lateral movement of at least the second foil beam to alter the pitch distance between the first and second foil beams. In another embodiment, the mechanism of the foil beam assembly comprises a hydraulic or pneumatic device mounted on the first and second foil beams and operable to laterally move at least the second foil beam relative to the first foil beam. In another embodiment of the foil beam assembly, the mechanism can comprise an activating screw and nut assembly affixed to the second foil beam and oriented perpendicular to the foil beams, the activating screw connected to an actuating device operable to move the activating screw to laterally move the second foil beam relative to the first foil beam. In yet another embodiment, the mechanism of the foil beam assembly can comprise nut members mounted on a surface of the first and second foil beams, and activating screw members engaged through the nut members and extending perpendicular to the foil beams, the activating screw members connected to actuators comprising a worm/gear assembly mounted on a drive shaft, wherein movement of the actuators move the activating screw members which laterally move at least the second foil beam relative to the first foil beam. Yet another embodiment of a mechanism for use in the foil beam assembly comprises a pantograph assembly connected to the first and second foil beams, wherein extension and retraction of the pantograph moves at least the second foil beam relative to the first foil beam to alter the pitch distance therebetween. A further embodiment of the mechanism of the foil beam assembly comprises a telescoping shaft assembly.

In another aspect, the invention provides a method of varying the frequency of a foil beam set. In one embodiment, the method comprises the steps of providing at least a first and second foil beam set, each set comprising two or more foil beams mounted on a support structure, and a mechanism interconnecting the foil beams and the foil beam sets, the mechanism structured to laterally move the foil beams relative to each other and to laterally move the foil beam sets relative to each other; and actuating the mechanism to laterally move the foil beams to alter the distance therebetween and maintain the foil beams at a distance X relative to each other, and to laterally move the foil beam sets relative to each other to a distance as an integer multiple of the distance X, wherein the combined frequency of the foil beam sets is maintained at about 50 to about 90 hertz.

In another aspect, the invention provides an assembly for dewatering a suspension in a papermaking apparatus. In one embodiment, the assembly comprises first and second sets of dewatering elements mounted on a support structure, at least one set including at least one foil element and at least one table roll, and an actuating mechanism interconnecting the dewatering elements and the sets and operable to laterally move and space apart the dewatering elements by a standard interval, and to laterally move at least one of the sets to space apart the sets by an integer multiple of the standard interval. In a method of varying the frequency of a set of dewatering elements, the actuating mechanism is activated to laterally move the dewatering elements relative to each other to a distance X and to laterally move the sets relative to each other to a distance as an integer multiple of the distance X.

In another embodiment of a foil assembly according to the invention, the assembly comprises at least one multi-surfaced foil element. In one embodiment, the multi-surfaced foil element comprises a unitary structure having two wire-contacting surfaces spaced apart by the standard interval X with a suction-forming section and a drainage section therebetween. Such a foil element is useful to achieve a pitch distance between wire contact surfaces of about 1 inch to up to 2-1/2 inches, although higher pitch distances can be used if desired. In an embodiment of a VF assembly, the assembly can comprise a multi-surfaced foil element in combination with a foil having a single wire contacting surface or other foil element, and/or a table roll or other dewatering element.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below with reference to the following accompanying drawings, which are for illustrative purposes only. Throughout the following views, the reference numerals will be used in the drawings, and the same reference numerals will be used throughout the several views and in the description to indicate same or like parts.

FIG. 1 is an illustration of a conventional Fourdrinier table assembly.

FIG. 2 is a perspective view of a conventional foil box having four foils.

FIG. 3 is a schematic top plan view of an embodiment of an assembly of variable frequency foil boxes according to the invention comprising a series of three foil sets (boxes), each foil set having six foils.

FIG. 4 is a schematic top plan view of the variable frequency foil box assembly of FIG. 3, showing foils having been removed from two foil sets.

FIG. 5 is a perspective, partial view of embodiment of a variable frequency foil box according to the invention utilizing a double acting screw mechanism to move the foil support beams.

FIG. 6 is a perspective view of another embodiment of a variable frequency foil box according to the invention utilizing a foil box arrangement using a hydraulic/pneumatic cylinder mechanism to move the foil support beams.

FIG. 7 is a perspective view of another embodiment of a variable frequency foil box according to the invention utilizing a multiple lead screw mechanism to move the foil support beams.

FIGS. 8A-8C are illustrations of another embodiment of a variable frequency foil box according to the invention utilizing pantograph assemblies to move the foil support beams. FIG. 8A is a top perspective view of the variable frequency foil box. FIG. 8B is a bottom plan view of the variable frequency box of FIG. 8A, taken along lines A--A, and showing the attachment of the foil support beams to the center points of the underlying pantograph assembly. FIG. 8C is a side elevational view of the variable frequency box of FIG. 8B, taken along lines B--B.

FIGS. 9A-9B are top and bottom perspective views, respectively, of another embodiment of a variable frequency foil (VFF) box according to the invention assembled with a second set of foils, showing the leading and trailing foil beams of each set mounted on linear rails, and utilizing pantograph assemblies, right-angle gearboxes and lead screw assemblies to move the foil support beams.

FIG. 10 is another embodiment of a variable frequency foil box of the invention illustrating a rack and pinion gearing mechanism that can be utilized to establish and maintain equidistant spacing between adjacent foil beams.

FIG. 11 is a perspective view of an embodiment of a variable frequency dewatering assembly according to the invention comprising dewatering elements in the form of foil beams and a table roll mounted on linear rails.

FIG. 12 is a perspective view of an embodiment of a table roll as used in the assembly in FIG. 11.

FIG. 13 is a partial side elevational view of the table roll of FIG. 12

FIG. 14 is an end view of the table roll of FIG. 13, taken along line 14--14.

FIG. 15 is a cross-sectional view of the table roll of FIG. 13, taken along line 15--15.

FIG. 16 is a partial perspective view of an embodiment of a multi-surfaced foil element according to the invention.

FIG. 17 is a cross-sectional view of the foil element of FIG. 16 taken along line 17--17, showing a moving wire in contact with the surfaces of the foil element.

FIG. 18 is cross-sectional view of two multi-surfaced foil elements placed in an assembly.

FIG. 19 is a sectional view of an embodiment of a prior art adjustable angle foil.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to mechanisms and methods for varying the frequency of a Fourdrinier table, independent of the wire speed, by continuously and uniformly adjusting the pitch distances of individual foils within foil sets over a finite range, and also adjusting the distance between foil sets (boxes). The mechanisms of the invention can be used in gravity box sections of the infeed end of a paper machine Fourdrinier table, among other applications. The invention will be described generally with reference to the drawings for the purpose of illustrating the present preferred embodiments only and not for purposes of limiting the same.

An assembly 37' comprising three variable frequency foil (VFF) boxes ("foil sets") 36a', 36b', 36c' for use in a Fourdrinier table, is illustrated in FIG. 3. As typical, each VFF foil set 36a'-36c' incorporates up to six foils 38' (38'a-c, 1-6) affixed to individual foil support beam structures 40' (40'a-c, 1-6), although an individual foil set can comprise more or less foils as desired. The width 42' of the foil boxes 36a'-36c' corresponds to the width of the paper making machine. The foil support beams 40' are mounted so as to prevent movement along their respective centerlines 44', and to provide free movement along an axis perpendicular to their respective centerlines.

Utilizing a mechanism according to the invention, the frequency of an individual foil box or set 36a'-36c' ("box frequency") is infinitely adjustable over a finite range by altering the pitch distance between the foil blades 38' within a foil set such that all the foils remain substantially equally spaced at a distance "X" throughout the adjustment range. According to the invention, in addition to maintaining a spacing of "X" between the foils/foil beams within a single foil set 36a'-36c' the relative distance between adjacent foil sets is also maintained at a standard interval (e.g., the foil spacing distance "X") or an integer multiple of that standard interval to sustain the desired frequency of the Fourdrinier table as a whole ("table frequency" or "Fourdrinier frequency"). For example, referring to foil sets 36a' and 36b', if the standard interval between foil support beams 40a1'-40a6' is X-inch (e.g., 5/4-inch), then the distance between the last (trailing) foil beam 40a6' on the first foil set 36a' and the leading foil beam 40b1' on the next (second) foil set 36b' would be either 1X, 2X, 3X-inch, etc. (51/4, 101/2, 153/4-inch, etc.), and the distance between the last (trailing) foil beam 40a6' on the second foil set 36a' to the leading foil beam 40c1' on the next (third) foil set 36c' would also be either 1X, 2X, 3X-inch etc. (51/4, 101/2, 153/4-inch, etc.), and so forth. This is accomplished by altering the distances between adjacent foil sets (36a' to 36b', 36b' to 36c') utilizing a mechanism according to the invention. As depicted in FIG. 3, the standard interval between foils is "X", and the distance between foil sets is "2X".

In addition, one or more of the foil support beams 40' within a foil set can be removed to effect desirable changes to the rate at which water is drained from the stock. For example, as depicted in FIG. 4, the fourth foil beam 40a4' has been removed from the first foil set 36a', and foil beams 40b4' and 40c2' have been removed from the second and third foil sets 36b', 36c', respectively. Removal of foil beams preferably does not alter the Fourdrinier frequency once established. Removal of every other foil beam in a foil set results in a 2X spacing between foil beams and a frequency that is one-half of that achievable with a foil set in which all six foil beams 40' are provided at a spacing of "X".

The table frequency or Fourdrinier frequency is altered as a function of wire speed and foil pitch distance according to the following formula: ##EQU1##

Table 1 shows the Fourdrinier frequencies over a range of wire speeds and foil pitch distances, which is preferably about 50 hertz to about 90 hertz.

TABLE 1 Fourdrinier Frequency as a Function of Wire Speed and Foil Pitch Distance Foil ft/min in/sec Pitch 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 500.00 100.00 100.00 80.00 66.67 57.14 50.00 44.44 40.00 36.36 33.33 30.77 27.59 26.67 25.00 600.00 120.00 120.00 96.00 80.00 68.57 60.00 53.33 48.00 43.64 40.00 36.92 34.29 32.00 30.00 700.00 140.00 140.00 112.00 93.33 80.00 70.00 62.22 56.00 50.91 46.67 43.08 40.00 37.33 35.00 800.00 160.00 160.00 128.00 106.67 91.43 80.00 71.11 64.00 58.18 53.33 49.23 45.71 42.67 40.00 900.00 180.00 180.00 144.00 120.00 102.86 90.00 80.00 72.00 65.45 60.00 55.38 51.43 48.00 45.00 1000.00 200.00 200.00 160.00 133.33 114.29 100.00 88.89 80.00 72.73 66.67 61.54 57.14 53.33 50.00 1100.00 220.00 220.00 176.00 146.67 125.71 110.00 97.78 88.00 80.00 73.33 67.69 62.86 58.67 55.00 1200.00 240.00 240.00 192.00 160.00 137.14 120.00 106.67 96.00 87.27 80.00 73.85 68.57 64.00 60.00 1300.00 260.00 260.00 208.00 173.33 148.57 130.00 115.56 104.00 94.55 86.67 80.00 74.29 69.33 65.00 1400.00 280.00 280.00 224.00 186.67 160.00 140.00 124.44 112.00 101.82 93.33 86.15 80.00 74.67 70.00 1500.00 300.00 300.00 240.00 200.00 171.43 150.00 133.33 120.00 109.09 100.00 92.31 85.71 80.00 75.00 1600.00 320.00 320.00 256.00 213.33 182.86 160.00 142.22 128.00 116.36 106.67 98.46 91.43 85.33 60.00 1700.00 340.00 340.00 272.00 226.67 194.29 170.00 151.11 136.00 123.64 113.33 104.62 97.14 90.67 85.00 1800.00 360.00 360.00 288.00 240.00 205.71 180.00 160.00 144.00 130.91 120.00 110.77 102.86 96.00 90.00 1900.00 380.00 380.00 304.00 253.33 217.14 190.00 168.89 152.00 138.18 126.67 116.92 108.57 101.33 95.00 2000.00 400.00 400.00 320.00 266.67 228.57 200.00 177.78 160.00 145.45 133.33 123.08 114.29 106.67 100.00 2100.00 420.00 420.00 336.00 280.00 240.00 210.00 186.67 168.00 152.73 140.00 129.23 120.00 112.00 105.00 2200.00 440.00 440.00 352.00 293.33 251.43 220.00 195.56 176.00 160.00 146.67 135.38 125.71 117.33 110.00 2300.00 460.00 460.00 368.00 306.67 262.86 230.00 204.44 184.00 167.27 153.33 141.54 131.43 122.67 115.00 2400.00 480.00 480.00 384.00 320.00 274.29 240.00 213.33 192.00 174.55 160.00 147.69 137.14 128.00 120.00 2500.00 500.00 500.00 400.00 333.33 285.71 250.00 222.22 200.00 181.82 166.67 153.85 142.86 133.33 125.00 2600.00 520.00 520.00 416.00 346.67 297.14 260.00 231.11 208.00 189.09 173.33 160.00 148.57 138.67 130.00 2700.00 540.00 540.00 432.00 360.00 308.57 270.00 240.00 216.00 196.36 180.00 166.15 154.29 144.00 135.00 2800.00 560.00 560.00 448.00 373.33 320.00 280.00 248.89 224.00 203.64 186.67 172.31 160.00 149.33 140.00 2900.00 580.00 580.00 464.00 386.67 331.43 290.00 257.78 232.00 210.91 193.33 178.46 165.71 154.67 145.00 3000.00 600.00 600.00 480.00 400.00 342.86 300.00 266.67 240.00 218.18 200.00 184.62 171.43 160.00 150.00 3100.00 620.00 620.00 496.00 413.33 354.29 310.00 275.56 248.00 225.45 206.67 190.77 177.14 165.33 155.00 3200.00 640.00 640.00 512.00 426.67 365.71 320.00 284.44 256.00 232.73 213.33 196.92 182.86 170.76 160.00 3300.00 660.00 660.00 528.00 440.00 377.14 330.00 293.33 264.00 240.00 220.00 203.08 188.57 176.00 165.00 3400.00 680.00 680.00 544.00 453.33 388.57 340.00 302.22 272.00 247.27 266.67 209.23 194.29 181.33 170.00 3500.00 700.00 700.00 560.00 466.67 400.00 350.00 311.11 280.00 254.55 233.33 215.38 200.00 186.67 175.00 3600.00 720.00 720.00 576.00 480.00 411.43 360.00 320.00 288.00 261.82 240.00 221.54 205.71 192.00 180.00 3700.00 740.00 740.00 592.00 493.33 422.86 370.00 328.89 296.00 269.09 246.67 227.69 211.43 197.33 185.00 3800.00 760.00 760.00 608.00 506.67 434.29 380.00 337.78 304.00 276.36 253.33 233.85 217.14 202.67 190.00 3900.00 780.00 780.00 624.00 520.00 445.71 390.00 346.67 312.00 283.64 260.00 240.00 222.86 208.00 195.00 4000.00 800.00 800.00 640.00 533.33 457.14 400.00 355.56 320.00 290.91 266.67 246.15 228.57 213.33 200.00 4100.00 820.00 820.00 656.00 546.67 468.57 410.00 364.44 328.00 2