US3839149A

US3839149A - Headbox for cylinder papermaking machine having flexible trailing elements therein and a flexible slice roof of tapering thickness

Info

Publication number: US3839149A
Application number: US00172822A
Authority: US
Inventors: E Justus; A Roerig
Original assignee: Beloit Corp
Current assignee: Beloit Corp
Priority date: 1971-08-18
Filing date: 1971-08-18
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01
Also published as: IT963930B; DE2240596A1; JPS4828702A; CA964089A; GB1394167A; ES405634A1

Abstract

A cylinder-type papermaking machine for forming a paper web such as grades of board including a pressure headbox on the uprunning side of the porous cylinder having a plurality of flexible upstream anchored trailing self-positionable members in the headbox with the headbox having a lower slice wall, an upper slice wall, and a forming zone roof member extending from the upper slice wall along the uprunning side of the cylinder. The forming zone roof member is flexible and tapers in thickness in the downstream direction. Hinges and jacks operate to adjust the positioning of the upper slice wall as well as the curvature of the forming zone roof member.

Description

HEADBOX FOR CYLINDER PAPERMAKING MACHINE HAVING FLEXIBLE TRAILING ELEMENTS THEREIN AND A FLEXIBLE SLICE ROOF OF TAPERING THICKNESS BACKGROUND OF THE INVENTION The invention relates to improvements in forming machines of the type wherein fiber carrying stock is fed onto the surface of a porous rotating roll and the stock is dewatered through the roll to form a web on its surface. The instant invention relates to improvements in web formers of this type known as hydraulic formers wherein the stock is fed onto the surface of the roll at a pressure to increase the rate of dewatering and improvements are provided for a more rapid, more satisfactory forming process wherein a variety of types of stocks having different fibers and different consistencies can be satisfactorily handled.

In a hydraulic former, stock is brought onto the surface of the uprunning side of a porous roll by a pressure headbox. The satisfactory formation of a uniform web having uniformly dispersed and random oriented fibers depends upon a number of factors including the drainage rate profile of the stock during the time it is fed onto the rotating porous roll. Where a plate or roof is provided to guide the flow of stock onto the surface under pressure, the liquid stock is constrained by the roof until the web is formed. During the time the stock is held between the roof and the roll, the space between the roof and the roll must diminish in a tapered forming area at the rate of drainage of water into the roll. This will vary with consistency and types of stocks, pressures and rates of flow so that constructions heretofore available have provided difficulty in retaining a satisfactory web under variant conditions. These variant conditions include types and consistencies of stock, speed of formation, headbox pressures and other factors.

It is accordingly an object of the present invention to provide an improved hydraulic headbox which provides substantial operational improvements over press sure headboxes for hydraulic formers heretofore available in being able to accommodate variations in formation conditions and yet obtain optimum formation of a web.

A still further object of the invention is to provide an improved hydraulic headbox which enables the formation of a better web and provides factors of adjustment which enables uniform random orientation and dispersement of the fibers.

A further factor to be taken into consideration in the formation of a web in a hydraulic headbox is the condition of the stock as it arrives at the forming roll. Random nonuniform dispersion of fibers, orientation of fibers either in a cross-machine or in a machine direction, and flocculation of the fibers all contribute to making a web of reduced quality. It has been difficult from machines heretofore available to maintain uniform dispersion of fibers in the stock in the relatively slower flow rates which occur in a cylinder forming machine of the type above described wherein the web is formed on a porous roll. Efforts have been concentrated to a large extent on the provision of uniform distribution of fibers in high speed fourdrinier machines, however, it has not been as critical to obtain uniform fiber dispersion in a cylinder type machine, but it has been known that uniform proper dispersion will provide improved formation. By attaining the improved level of stock and the improved formation on a cylinder type machine, better webs and better boards can be made, and the strength of such webs can be increased for any given type of stock.

It is accordingly an object of the present invention to provide an improved headbox construction for the delivery of uniform well dispersed stock to the cylinder of a forming machine.

A feature of the present invention is the provision of stock to the slice on a cylinder forming machine with the fibers uniformly dispersed and to provide a pressure forming zone wherein the roof is flexible and adjustable from its leading edge to its trailing edge so that the slice opening and the distance of the roof at its trailing edge can be independently adjusted and the curvature of the forming zone can be independently adjusted so that the forming zone can be adjusted in accordance with the drainage rate profile for optimum formation of the web.

A still further object of the invention is to provide an improved hydraulic cylinder forming machine which has improved features of construction and is more compact than structures heretofore available.

Other objects, advantages and features will become more apparent with the teachings of the principles of the present invention in connection with the disclosure of the preferred embodiments thereof in the claims, specification and drawings and it will be apparent to those versed in the art that various embodiments and modifications may be employed within the spirit and scope of the invention.

DESCRIPTION OF THE DRAWINGS The FIGURE is a side elevational view shown partially in section of the forming section of a hydraulic former constructed and operating in accordance with the principles of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As illustrated in the FIGURE, the cylinder forming machine includes a porous rotatable forming cylinder 10. This is a perforate shell and the water from the stock supplied to a forming zone 25 on the uprunning side passes into the center of the cylindrical roll and is removed. The shell of the forming cylinder 10 also may be provided as an open suction roll with a suction gland extending throughout the forming zone 25 up to the felt I].

The web formed on the uprunning side of the cylinder 10 is couched off onto a felt 11, and the felt may carry one or more additional layers of web formed by other formers along the line of the machine.

The stock is supplied to the cylinder 10 by a pressure headbox 13. The stock is received from a stock supply including a fan pump to a header chamber 14 of the headbox. From the header chamber 14, the stock flows through a plurality of parallel cylindrical headbox tubes 15. In the header 14 the fibers of the stock are well dispersed and stock is in turbulence with the turbulence being reduced from larger scale turbulence to smaller scale turbulence through the tubes 15 retaining the fibers in random orientation.

Following the tubes 15 the stock flows into a slice chamber 130 which is tapered and is formed by a lower slice wall 18 and an upper slice wall 20, with the upper slice wall facing toward the cylinder 10. The slice chamber is provided with flexible elements 16 which further reduces the scale of turbulence. The stock emerges into the forming zones 25 through a slice opening 13b. At the lower portion of the slice opening is an apron 19 which is rigidly secured to the trailing edge of the stationary lower slice wall 18, and the stock is fed onto the surface of the cylinder at the trailing edge of the apron 19.

The upper slice wall is preferably pivotally mounted and is movable to change the size of the slice opening 13b. A preferred form of hinge is shown at 21 formed of relatively stiff plastic which rigidly supports the loca tion of the upstream edge 20b of the upper slice wall 20 and permits the downstream edge 20c to pivotally move relative to the apron 19. The hinge 21 may be formed of reinforced plastic such as fiberglas. As illustrated in the drawing, the plastic hinge 21 is suitably bolted to the headbox and to the slice wall 20 to provide a smooth flow surface which will not catch and retain fibers of the stock and which accommodates a smooth flow pattern for the stock.

lt has been discovered that the scale of turbulence within the stock can be further reduced to provide and maintain well dispersed and random orientation of the fibers by providing flexible trailing members 16 within the elongate tapered slice chamber 13a. The trailing members 16 are flexible, and are preferably in continuous sheet form extending continuous in a crossmachine direction. In an alternative form, the flexible trailing members 16 may be in the form of numerous divided filaments. It has generally been discovered that ordinary separations or divisions in the sheets 16 which provide communication between the chambers between the sheets will cause flow ridges or flow streams that continue on through the forming zone so as to cause ridges in the formed web. In other words, with the sheets 16 or with multiple filaments, the separate flow streams of stock will retain their fine scale turbulence and the fibers will not orient in a cross-machine direction or in a machine direction as they flow through the tapered slice chamber 13a. It has also been discovered that the number of flexible trailing sheets 16 should preferably be limited in number. The taper of the elongate slice chamber 13a should be no less than 3.

The forming zone is formed between the surface of the cylinder 10 and a slice roof 22. The roof 22 is formed of a flexible material such as fiberglas or reinforced plastic which has sufficient rigidity to retain its shape under the pressures experienced from the stock in the forming chamber 25, but which will change shape from forces applied such as to the upstream edge 22a and downstream edge 22b of the roof 22. This roof of fiberglas or reinforced plastic is less expensive to manufacture and easier to form into the specific shape required.

The roof is mounted at its upstream edge 22a on the downstream edge of the slice roof 20. The entire roof is supported on a cross-machine beam 26. The beam is mechanically positioned by a hydraulic or mechanical actuator 27 which is shown schematically. The position of this beam 26 determines the overall position of the roof 22 relative to the surface of the cylinder 10, and also the overall position of the downstream edge of the upper slice wall 20. Movement of the beam will change the space 13b and thus the flow of stock without changing the curvature of the roof 22.

Additional adjustment means are provided for adjusting the position of the upstream edge 22a and the downstream edge 22b of the roof. These are in the form of force applying members, including a jack 23 which is connected between the beam 26 and the upstream edge 22a of the roof 22. A jack 24 is connected between the beam 26 and the downstream edge 22b of the roof.

Adjustment of the upstream jack 23 will change the slice opening and the rate at which the stock is fed into the forming zone 25. Adjustment of the downstream jack 24 will change the spacing between the downstream edge 22b of the roof relative to the cylinder 10.

The upstream edge 22a and the downstream edge 22b of the roof 22 are supported so that the roof bends as the edges are moved. In other words, as the downstream edge 22b is moved toward or away from the roll, the upstream edge 22a is in effect cantilever supported so that bending will occur along the length of the roof 22. Similarly, the downstream end 22b of the roof is rigidly held so that the roof bends along its length as the other edge 22a is moved toward or away from the roll.

The roof 22 is also designed to vary in strength along its length so that for range of positions of the upstream edge 22a, and the range of positions of the downstream edge 22b, the roof will be bent to maintain an optimum shape and taper of the forming zone 25. As illustrated in the drawings, the design of the roof strength requires a taper in a downstream direction. The roof will be designed in strength to change curvature as the upstream of trailing edges of the roof are moved and to maintain a forming zone of optimum shape. That is, the drainage rate profile along the forming zone will change and remain optimum along the length of the roof with change in slice opening leading to the forming zone or with change in the position of the trailing edge of the roof.

We claim as our invention:

1. In a machine for forming a web from a fiber containing stock, the combination comprising,

a rotatable porous forming roll for draining water from a slurry of stock deposited on the surface thereof and forming a web, a headbox for receiving stock under pressure extending along the roll and having a lower wall and an upper wall facing the roll and having a slice opening,

said upper wall pivotally supported at its upstream edge,

a curved roof member nonrigid in the direction of curvature mounted on the upper wall extending from the slice opening along the surface of the forming roll, and

means for varying the curvature of said roof member during operation, including first and second power means at the leading and trailing edges of said roof member moving away from the roll along paths which extend in a converging angle toward each other so that said roof member bends and changes curvature about its length as it is moved toward or away from the roll.

2. In a machine for forming a web from a fiber containing stock, the combination comprising,

a rotatable porous forming roll for draining water from a slurry of stock deposited on the surface thereof and forming a web,

a headbox for receiving stock under pressure extending along the roll with a lower wall and an opposing upper wall facing the roll and having a slice opening at the downstream edges with the downstream edges extending substantially the same distance in the direction of the flow stream,

a pivotal support for the upstream edge of the upper wall, said upper wall being rigid to be positioned by movement of its downstream edge,

a curved roof member tapered in a downstream direction extending from the slice opening along the surface of the forming roll and pivotally attached to the downstream edge of the upper wall, the roof member having a predetermined curvature for optimum flow characteristics between the roof and forming roll,

a cantilever support for one end of the roof member, and an adjustment means connected to the other end of the roof member for moving it toward or away from the roll to bend it about the cantilever support so that its curvature changes in different amounts along its length.

3. In a machine for forming a web from a fiber containing stock constructed in accordance with claim 2, the combination wherein said roof member is cantilever supported at its upstream end, and the profile of the roof member is tapered along its length from an upstream to a downstream direction so that the forming zone between the roof member and roll will retain an optimum shape with changes in position of the downstream end of the roof member.

4. In a machine for forming a web from a fiber containing stock constructed in accordance with claim 2, the combination wherein said adjustment means and cantilever support include first force means for moving the upstream edge of said roof member toward or away from the roll, a second force means for moving the downstream edge of said roof member toward or away from the roll, and a third force member connected to both of said first and second force means for moving the entire roof member relative to the forming roll.

5. In a machine for forming a web from a fiber containing stock constructed in accordance with claim 2, wherein said adjustment means and cantilever support include a first support at the upstream edge of said roof, a second support at the downstream edge of said roof, and each support being rigidly connected to the roof so that as either support is moved in a direction toward or away from the roll the roof will bend about the other support, and first and second power means respectively connected to said supports for moving said supports in a direction toward or away from said forming roll.

6. In a machine for forming a web from a fiber containing stock, the combination constructed in accordance with claim 2, including a plurality of trailing flexible members extending in a cross-machine direction parallel to the roll within said headbox anchored at their upstream ends with their downstream edge selfpositioned by forces of the stock flowing through the headbox.

7. In a machine for forming a web from a fiber containing stock constructed in accordance with claim 6, the combination including a plurality of elongate passages extending parallel to the flow of stock through the headbox positioned upstream of said flexible members.

8. In a machine for forming a web from a fiber containing stock constructed in accordance with claim 6, the combination wherein said flexible members are continuous in a cross-machine direction.

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Claims

1. In a machine for forming a web from a fiber containing stock, the combination comprising, a rotatable porous forming roll for draining water from a slurry of stock deposited on the surface thereof and forming a web, a headbox for receiving stock under pressure extending along the roll and having a lower wall and an upper wall facing the roll and having a slice opening, said upper wall pivotally supported at its upstream edge, a curved roof member nonrigid in the direction of curvature mounted on the upper wall extending from the slice opening along the surface of the forming roll, and means for varying the curvature of said roof member during operation, including first and second power means at the leading and trailing edges of said roof member moving away from the roll along paths which extend in a converging angle toward each other so that said roof member bends and changes curvature about its length as it is moved toward or away from the roll.

2. In a machine for forming a web from a fiber containing stock, the combination comprising, a rotatable porous forming roll for draining water from a slurry of stock deposited on the surface thereof and forming a web, a headbox for receiving stock under pressure extending along the roll with a lower wall and an opposing upper wall facing the roll and having a slice opening at the downstream edges with the downstream edges extending substantially the same distance in the direction of the flow stream, a pivotal support for the upstream edge of the upper wall, said upper wall being rigid to be positioned by movement of its downstream edge, a curved roof member tapered in a downstream direction extending from the slice opening along the surface of the forming roll and pivotally attached to the downstream edge of the upper wall, the roof member having a predetermined curvature for optimum flow characteristics between the roof and forming roll, a cantilever support for one end of the roof member, and an adjustment means connected to the other end of the roof member for moving it toward or away from the roll to bend it about the cantilever support so that its curvature changes in different amounts along its length.

6. In a machine for forming a web from a fiber containing stock, the combination constructed in accordance with claim 2, including a plurality of trailing flexible members extending in a cross-machine direction parallel to the roll within said headbox anchored at their upstream ends with their downstream edge self-positioned by forces of the stock flowing through the headbox.