US3907635A

US3907635A - Adjustable drain plate in a paper web forming zone

Info

Publication number: US3907635A
Application number: US536233A
Authority: US
Inventors: David J Bringman
Original assignee: Beloit Corp
Current assignee: Beloit Corp
Priority date: 1973-03-27
Filing date: 1974-12-24
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23

Abstract

A mechanism and method for forming a web from a fibrous stock slurry with a traveling fourdrinier wire for receiving a slurry from a headbox having upper and lower slice lips in close proximity to the wire with the upper lip on a pivotal forming roof which is pivoted on another portion of the roof to provide an adjustable throat and a plate adjustable in the machine direction beneath the wire and movable across the slice opening to control the length of the drainage zone and the location of the dry line on the wire.

Description

United States Patent [1 1 Bringman Sept. 23, 1975 1 1 ADJUSTABLE DRAIN PLATE IN A PAPER WEB FORMING ZONE [75] Inventor: David J. Bringman, Beloit, Wis.

[73] Assignee: Beloit Corporation, Beloit, Wis.

[22] Filed: Dec. 24, 1974 [21] Appl. No.: 536,233

Related U.S. Application Data [63] Continuation of Ser. No. 345.324, March 27. 1973,

3.190.790 6/1965 Ploetz et a1. 162/212 3.3571180 12/1967 Curtis 1. 162/350 X 3,676,294 7/1972 Opderbeck ct a1; 1. 162/350 X 3,764,465 10/1973 Bartley et al. i v. 162/351 3,775,244 11/1973 Hubschmann 162/351 Primary ExaminerS. Leon Bashore Assistant Examiner-Richard V. Fisher Attorney, Agent, or FirmHill, Gross. Simpson, Van Santen, Steadman, Chiara & Simpson [5 7] ABSTRACT A mechanism and method for forming a web from a fibrous stock slurry with a traveling fourdrinier wire for receiving a slurry from a headbox having upper and lower slice lips in close proximity to the wire with the upper lip on a pivotal forming roof which is pivoted on another portion of the roof to provide an ad justable throat and a plate adjustable in the machine direction beneath the wire and movable across the slice opening to control the length of the drainage zone and the location of the dry line on the wire.

9 Claims, 2 Drawing Figures US Patent Sept. 23,1975

02 Y L //VE ADJUSTABLE DRAIN PLATE IN A PAPER WEB FORMING ZONE This is a continuation of application Ser. No. 345,324, filed Mar. 27, 1973, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to improvements in methods and mechanisms for the continuous pressure forming of nonwoven synthetic webs or paper webs or a combination thereof, and particularly to an arrangement for controlling the rate of water tain an improved web. 7

In the formation of a web a fibrous slurry of stock is pressure discharged onto a traveling wirefrom a headbox having a slice opening exposed to the wire for a distance. Beyond the headbox a dry line appears on the wire to indicate the end of the drainage zone. As is recognized by paper makers, the dry line is a phenomena which provides a visible line across the forming wire that enables the paper maker to adjust the machine for uniform basis weight across the machine width.

A feature of the invention is to provide a pressure full hydraulic headbox which is positioned to'be angled upwardly to prevent the formation of air pockets in the flowing stock. A further feature of the invention is the provision of an upwardly inclined-traveling wire receiving the stock from the slice opening with the headbox having a forming roof over the forming zone of the wire.

In forming the web with cellulose or synthetic fibers with a pressure headbox and a roof extending over the drainage zone, it has been discovered thatin this type of structure for optimum formation it is imperative that free water is discharged from the distal edge of the upper slice lip to the extent that the gap between the forming wire and the slice lip is fully occupied by the partially formed web and water. It is also desirable to maintain the free water discharge from the slice tip at a minimum in order to effect a dry line or formed sheet as soon after the slice discharge as feasible. Excess free water discharge from the slice can effect poor formation partly due to the tendency of the water to adhere upwardly toward the slice tip while the partial formed web adheres to the forming wire traveling therebe neath. This creates a void or air entrainment between the free water and partially formed web.

The upwardly traveling forming wire must be maintained at an angle which is critical in that it is desirable to maintain an upward flow through the headbox inlet, body and slice to avoid the creation of air pockets. A horizontal or level wire system would be feasible if an air bleed arrangement is utilized at the high point of the headbox system.

It has been discovered that factors affecting the amount of free water discharge from the slice of the forming roof are: i t

1. Slice opening.

2. Stock consistency and freeness.

3. Pressure differential across the wire which is dependent upon the stock head and drainage device vacuum beneath the wire.

4. Resistance to flow of water through the forming wire.

5. Resistance of flow of water through the'partially formed mat or web.

6. Stock temperature,- viseosity and other factors affecting flow.

drainage to ob- 7. Drainage area or drainage zone length.

ln-the formation of nonwoven webs wherein synthetic fibers are used and in the formation of free draining cellulose fiber blends and on certain paper grades, it is desirable to operate the headbox for inlet water rates over a large range of volumes. This range can vary from 2 to l on paper grades up to 10 to l or higher for nonwoven grades containing at least a portion of synthetic fibers. In the manufacture of nonwoven webs by web processes, the entering stock consistency requirement and resulting water rate is largely dependent on fiber length. The longer the fiber, the lower the consistency, or in other words, the higher the water rate required. Water rate requirements and resulting drainage requirements will vary for nonwoven webs with fiber length and will vary with paper or paper combined with nonwoven blends with fiber characteristics, stock freeness, stock consistency, and change in basis weights and machine speeds.

In the wet process manufacture of paper or nonwoven webs or blends thereof, as stated, it is important to maintain a minimum of free water discharge from the roof slice tip and it is important to control the water rate through the headbox and onto the forming wire for various furnishes, basis weights and machine speeds. The drainage rate through the forming wire must also be variable in direct proportion to the headbox flow rates. It isalso desirable that the drainage rate change be controllable in a short time, preferably during operation of the machine. One method of varying the drainage rate is by changing the pressure differential across the web by change of vacuum in the vacuum box or drainagedevice beneath the wire. Some control can be obtained by this means, but sufficient changes in drainage cannot be obtained solely by this means to match headbox water rate changes, particularly with free draining cellulose stocks and synthetic fiber furnishes of low consistency. Sufficient control also cannot be obtained over moderate to extreme basis weight changes.(at constantspeed) or speed changes (at constant basis weight). Also, sufficient control cannot be maintained with changes in speed and basis weight that simultaneously increase or decrease water rate requirements.

It is accordingly a. feature of the present invention to provide a method and mechanism of varying the drainage rate through a continuous traveling forming wire when delivering the stock to the forming wire under a forming roof such that pressure formation will be utilized. The invention embodies a drainage device plate or cover and a supporting member incorporating a vacuum box with compartmented drop legs for vacuum retention and connection for vacuum pumps. The drainage device cover or plate is adjustable in position in the machine direction to vary the effect of slice opening and to vary the length of the drainage zone. This arrangement allows for infinite adjustment within the maximum outer limits of the slice opening, i.e., drainage area.

It is accordingly an object of the present invention to provide an improved pressure forming arrangement wherein the water drainage can be readily controlled during operation so that a wide variety of operating conditions can be accommodated.

A further object of the present invention is to provide an improved pressure formation structure for forming a traveling web from a stock slurry wherein various flow factors through the headbox can be changed for optimum web formation and the water drainage independently controlled by an improved arrangement for varying the water drained through the forming surface.

Other objects, advantages and features, as well as equivalents thereof which are intended to be covered herein, will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments in the specification, claims, and drawings, in which:

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view shown schematically, partially in section, of an arrangement constructed and operated in accordance with the principles of the present invention; and

FIG. 2 is a similar side elevational view showing the parts adjusted to another position.

DESCRIPTION As shown in FIGS. 1 and 2, the mechanism includes a pressurized stock supply inlet leading to a pressure headbox 11 which extends in an upwardly inclined direction so as to avoid the formation of air bubbles in the flowing stock. The stock is deposited on a traveling forming surface in the form of a fourdrinier wire 12 which extends in an upwardly inclined direction in the forming run with the inclined direction being provided so as to accommodate the upward inclination of the headbox. The wire is supported on suitable rolls including a breast roll 13.

The headbox has a slice opening 14 where the stock is exposed to the traveling wire to provide a pressure formation slice opening. The slice opening extends from the distal edge of the lower slice lip 15 to the distal edge of the upper slice lip 17. The upper slice lip is at the edge of the upper forming roof 16 which is pivotally mounted on the headbox at a pivot point 18. Power means such as jack screws shown schematically at 22 are provided for moving the forming roof up or down to control the space between the slice lip 17 and the wire 12.

The forming roof 16 is supported on a roof extension 19 which is part of the top of the headbox and which is pivoted at 20. By moving the roof extension 19 up or down, the size of the throat of the headbox leading to the slice chamber can be adjusted, and this is accomplished by power means shown schematically at 21 which may be in the form of jack screws or similar power adjustment members.

Beneath the wire is a suction box means 23 divided into compartments 23a, 23b. 23c and 23d. Beneath the wire at the topv of the suction box is a box top 29 which has suitable large openings for the water to freely pass through the wire and into the suction box. The suction box leads downwardly into a water collection container A suction pump 25 has a suction line 25a connected to the various compartments which may have individual valve controls so as to control the vacuum in each of the compartments. A normally increased vacuum will be applied in each successive compartment as the .thickness of the web builds up on the wire.

At the upstream end of the slice opening is a drainage plate or cover 26 which is adjustably movable across the slice opening to block drainage. The plate 26 is shown in the maximum open position in FIG. 1 and in the maximum closed position in FIG. 2. Power means I shown schematically at 27 are provided for moving this drainage blocking plate to the desired adjusted position. The plate is secured to the suction box 23 which 5 is also movable and a power means 28 will be provided which may be part of the power means 27 for shifting the box 23 and the plate 26 in the machine direction. Drainage will begin at the downstream edge of the plate 26 and the distance from this edge to the upper slice lip is the forming zone length. i

Following the downstream upper slice lip 17 a dry line 15a will appear. In accordance with the principles of the invention, the plate 26 will be adjusted in a positionrelative to the other factors of machine operation so as to maintain the dry line one-eighth to 5 inches beyond the upper slice lip 17, and preferably one-half to 3 inches.

Thus, a drainage zone will be formed. which will extend from the downstream edge 26a of the plate 26 to the dry line 15a the drainage distance being shown by the arrowed line 30 in FIG. 1, and by 30' in FIG. 2. The upper slice lip 17 will be positioned so that a minimum of. free water discharge from the roof past the slice lip will occur. The position of the plate will be set relative to the headbox flow rate so that the dry line occurs at the location above discussed, i.e., immediately downstream of the upper slice lip. The drainage rate must be controlled to match headbox water rate changes and absolute control is essential with free draining cellulose stocks and synthetic fiber furnishes of low consistency.

I claim as my invention:

l. The method of forming a web from a fibrous stock slurry with a mechanism' having a movable porous forming surface for receiving a slurry of stock and draining water therefrom to form a traveling web, the headbox having upper and lower slice lips in close proximity to the forming surface with the distance from the lower to the upper slice lip defining a machine direction slice opening along the forming surface and the 0 machine direction distance from the location where the water begins draining from the stock to the dry line defining a drainage zone, and having a drain plate means with an imperforate portion and a perforate portion opposite the slice opening with the imperforate portion blocking the slice opening to prevent flow through the forming surface with the imperforate portion being of v sufficient length to block the drainage zone for substantial lengths, the method including the steps of detera substantial distance beyond the lower slice lip to control the length of the drainage zone by moving the plate I to change the distance the imperforate portion extends in the machine direction to block controlled lengths of the slice opening to position the dry line a predetermined distance beyond the upper slice lip.

2. The method in accordance with claim 1 wherein: the upper slice lip is adjustable relative to the forming surface to control free water passing the upper slice lip. 3. The method in accordance with claim 1 wherein: the dry line is adjusted to extend one-eighth to 5 inches beyond the upper slice lip. 4. A mechanism for forming a web from a fibrous stock slurry comprising in combination:

a movable porous forming surface for receiving a slurry of stock and draining water therefrom to form a traveling web;

mining the dry line by blocking the forming surface for a headbox having a lower slice lip in close proximity 5. A mechanism for forming a web from a fibrous to the forming surface and having a roof extending stock slurry constructed in accordance with claim 4, over the forming surface with an upper slicc lip in including a suction box positioned beneath the form close proximity thereto, the distance from the ing surface with means to control the vacuum in lower to the upper slice lip defining a machine di- 5 said suction box. rection slice opening along the forming surface. a 6. A- mechanism for forming a web from a fibrous dry line appearing along the web on the forming stock slurry constructed in accordance with claim 4, surface downstream from the upper slice lip; wherein said headbox is angularly inclined upwardly. drain plate means extending beneath the forming sur- 7. A mechanism for forming a web from a fibrous face opposite the slice opening, said drain plate 10 stock slurry constructed in accordance with claim 4: means having an imperforate portion and a perfowherein said forming surface is a traveling wire. rate portion downstream therefrom relative to the 8. A mechanism for forming a web from a fibrous direction of forming surface travel, said imperforstock slurry constructed in accordance with claim 4: ate portion blocking drainage through the forming wherein said headbox has a forming roof extending surface and being of sufficient length to block the angularly upwardly above the wire and said roof drainage area for substantial lengths with machine being pivotal at its upstream edge to vary the disdirection movement of the plate means; tance between the upper slice lip and the wire. and means for moving said drain plate means in the 9. A mechanism for forming a web from a fibrous machine direction to increase the imperforate area stock slurry constructed in accordance with claim 8: and decrease the perforate area opposite the slice wherein said forming roof is hinged on a pivotal opening to controllably vary the length of time of headbox roof portion which is adjustable to vary drainage beneath the upper slice lip whereby the the size of a portion of the headbox leading to the plate can be adjusted to be a predetermined disslicc opening. tancc beyond the slice lip.

Claims

1. THE METHOD OF FORMING A WEB FROM A FIBROUS STOCK SLURRY WITH A MECHANISM HAVING A MOVABLE POROUS FORMING SURFACE FOR RECEIVING A SLURRY OF STOCK AND DRAINING WATER THEREFROM TO FORM A TRAVELLING WEB, THE HEADBOX HAVING UPPER AND LOWER SLICE LIPS IN CLOSE PROXIMITY TO THE FORMING SURFACE WITH THE DISTANCE FROM THE LOWER TO THE UPPER SLICE LIP DEFINING A MACHINE DIRECTION SLICE OPENING ALONG THE FORMING SURFACE AND THE MACHINE DIRECTION DISTANCE FROM THE LOCATION WHERE THE WATER BEINGS DRAINING FROM THE STOCK TO THE DRY LINE DEFINING A DRAINAGE ZONE, AND HVING A DRAIN PLATE MEANS WITH AN IMPERFORATE PORTION AND A PERFORATE PORTION OPPOSITE THE SLICE OPENING WITH THE IMPERFORATE PORTION BLOCKING THE SLICE OPENING TO PREVENT FLOW THROUGH THE FORMING SURFACE WITH THE IMPERFORATE PORTION BEING OF SUFFICIENT LENGTH TO BLOCK THE DRAINAGE ZONE FOR SUBSTANTIAL LENGTHS, THE METHOD INCLUDING THE STEPS OF DETERMINING THE DRY LINE BY BLOCKING THE FORMING SURFACE FOR A SUBSTANTIAL DISTANCE BEYOND THE LOWER SLICE LIP TO CONTROL THE LENGTH OF THE DRAINAGE ZONE BY MOVING THE PLATE TO CHANGE THE DISTANCE THE IMPERFORATE PORTION EXTENDS IN THE MACHINE DIRECTION TO BLOCK CONTROLLED LENTHS OF THE SLICE OPENING TO POSITION THE DRY LINE A PREDETERMINED DISTANCE BEYOND THE UPPER SLICE LIIP.

2. The method in accordance with claim 1 wherein: the upper slice lip is adjustable relative to the forming surface to control free water passing the upper slice lip.

3. The method in accordance with claim 1 wherein: the dry line is adjusted to extend one-eighth to 5 inches beyond the upper slice lip.

4. A mechanism for forming a web from a fibrous stock slurry comprising in combination: a movable porous forming surface for receiving a slurry of stock and draining water therefrom to form a traveling web; a headbox having a lower slice lip in close proximity to the forming surface and having a roof extending over the forming surface with an upper slice lip in close proximity thereto, the distance from the lower to the upper slice lip defining a machine direction slice opening along the forming surface, a dry line appearing along the web on the forming surface downstream from the upper slice lip; drain plate means extending beneath the forming surface opposite the slice opening, said drain plate means having an imperforate portion and a perforate portion downstream therefrom relative to the direction of forming surface travel, said imperforate portion blocking drainage through the forming surface and being of sufficient length to block the drainage area for substantial lengths with machine direction movement of the plate means; and means for moving said drain plate means in the machine direction to increase the imperforate area and decrease the perforate area opposite the slice opening to controllably vary the length of time of drainage beneath the upper slice lip whereby the plate can be adjusted to be a predetermined distance beyond the slice lip.

5. A mechanism for forming a web from a fibrous stock slurry constructed in accordance with claim 4, including a suction box positioned beneath the forming surface with means to control the vacuum in said suction box.

6. A mechanism for forming a web from a fibrous stock slurry constructed in accordance with claim 4, wherein said headbox is angularly inclined upwardly.

7. A mechanism for forming a web from a fibrous stock slurry constructed in accordance with claim 4: wherein said forming surface is a traveling wire.

8. A mechanism for forming a web from a fibrous stock slurry constructed in accordance with claim 4: wherein said headbox has a forming roof extending angularly upwardly above the wire and said roof being pivotal at its upstream edge to vary the distance between the upper slice lip and the wire.

9. A mechanism for forming a web from a fibrous stock slurry constructed in accordance with claim 8: wherein said forming roof is hinged on a pivotal headbox roof portion which is adjustable to vary the size of a portion of the headbox leading to the slice opening.