WO1990005210A1

WO1990005210A1 - Forming apparatus

Info

Publication number: WO1990005210A1
Application number: PCT/US1989/003847
Authority: WO
Inventors: Haruyoshi Fujiwara
Original assignee: Beloit Corporation
Priority date: 1988-10-31
Filing date: 1989-09-06
Publication date: 1990-05-17
Also published as: KR0121881B1; AU4307889A; CA1331531C; KR900702136A; MX172494B; ES2016767A6

Abstract

A forming apparatus (10) is disclosed for forming a web (W) from stock (S). The apparatus (10) includes in a headbox (12) for ejecting a jet (J) of the stock (S). A first and a second moving wire (14, 16) cooperate together to define therebetween a forming section (18) having a first and a second end (20, 22). The first end (20) of the forming section (18) is disposed closely adjacent to the headbox (12). A first plurality of shoes (24-33) cooperate with the first wire (14) such that water drains from the stock (S) through the first wire (14) and through a first plurality of channels (34-32) defined by the first plurality of shoes (24-33). A second plurality of shoes (44-53) cooperate with the second wire (16) such that water drains from the stock (S) through the second wire (16) and through a plurality of slots (54-62) defined by the second plurality of shoes (44-53). The first and the second plurality of shoes (24-33; 44-53) are staggered relative to each other for enhancing the dispersion of fibers within the stock (S) during formation of the web (W).

Description

A FORMING APPARATUS

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to a forming apparatus for forming a web from stock. More particularly, the present invention relates to a high consistency forming apparatus which enhances the dispersion of fibers within the stock during the formation of the web.

INFORMATION DISCLOSURE STATEMENT

In the past, various forming sections have been employed in an attempt to obtain adequate fiber dispersion when using a high consistency stock. However, such prior proposals have not been successful in providing the requisite degree of fiber dispersion and orientation.

The present invention seeks to enhance fiber dispersion in a high consistency stock by ejecting stock from a high consistency headbox between twin wires of a former passing around a pair of turning bars.

The lower wire passes over a plurality of solid shoes having drainage channels therebetween. The upper wire passes an equal number of upper solid shoes having upwardly extending drainage slots. The channels are disposed in staggered relationship relative to the slots and the shoes are arranged so that the wires extend in a curved configuration from the upstream to the downstream end of the forming section. The distance between the upper and the lower shoes can be adjusted to control the pressure pulses exerted on the stock. Additionally, at least two compartments in a machine direction are disposed beneath the lower wire and valves control the flow of white water from the stock passing between the wires so there exists a very controlled dewatering. forming apparatus includes a first turning bar which is disposed between the headbox and the first end of the fo'rming section such that the first wire extends around the first turning bar. Additionally, a second turning bar is disposed between the headbox and the first end of the forming section such that the second wire extends around the second turning bar. The arrangement is such that a jet of stock flows from the headbox to the forming section between the first and the second turning bars.

The forming section is curved in a direction from the first towards the second end thereof. The curved forming section is inclined upwardly from the first end towards the second end thereof with the forming section subsequently descending to the second end thereof such that the stock follows a curved path from the first to the second end of the forming section.

More specifically, the curved path is an arc which has a radius within the range 150 to 250 inches.

Each shoe of the first and second plurality of shoes is solid with each shoe of the first plurality of shoes defining a channel.

Similarly, each shoe of the second plurality of shoes defines a slot.

The number of shoes of the first plurality of shoes is equal to the number of shoes of the second plurality of shoes such that each shoe of the first and the second plurality of shoes is disposed in staggered relationship with each shoe defining a step.

Each shoe of the first plurality of shoes defines an inclined surface with the inclined surface being disposed in a plane which converges in a machine direction with the first wire, the surface extending from the channel to the first wire. Each shoe of the second plurality of shoes defines an inclined face with the inclined face being disposed in a plane which converges in a machine direction with the second wire. Each face extends from the slot to the second wire.

The forming apparatus includes means for adjusting the distance between the first and the second plurality of shoes for controlling the respective pressure pulses applied to the stock during passage of the stock through the forming section.

The forming apparatus also includes a pressure vessel connected to the channels and control means for controlling the flow of water through the channels.

More specifically, the pressure vessel includes a first and a second compartment disposed in a machine direction. The control means includes a first and a second control valve for controlling the flow of water from the first and the second compartments so that downward drainage in a machine direction can be controlled by the control valves.

The present invention also includes a method of forming a web from a high consistency stock. The method includes the steps: of ejecting a jet of the stock from a headbox;

moving a first and a second wire such that the wires cooperate together to define therebetween a forming section having a first and a second end, the first end of the forming section being disposed closely adjacent to the headbox;

moving the first wire over a first plurality of shoes such that water drains from the stock through the first wire and through a first plurality of channels defined by the first plurality of shoes; moving the second wire such that the second wire extends past a second plurality of shoes so that water drains from the stock through the second wire and through a plurality of slots defined by the second plurality of shoes; and

staggering the first plurality of shoes relative to the second plurality of shoes for enhancing the dispersion of fibers within the stock during the formation of the web.

Many modifications and variations of the present invention will be apparent to those skilled in the art by consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawing. Such modifications and variations fall within the spirit and scope of the present invention as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side-elevational view of a forming apparatus according to the present invention; and

Figure 2 is an enlarged elevational view of at least one shoe and channel as shown in figure 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 is a side-elevational view of a forming apparatus generally designated 10 for forming a web W from . stock S. The apparatus 10 comprises a headbox 12 for ejecting a jet J of the stock S.

A first and a second moving wire 14 and 16 respectively cooperate together to define therebetween a forming section 18 having a first and a second end 20 and 22 respectively. The first end 20 of the forming section 18 is disposed closely adjacent to the headbox 12. A first plurality of shoes 24, 25, 26, 27, 28, 29, 30,

31, 32 and 33 cooperate with the first wire 14 such that water drains from the stock S through the first wire 14 and through a plurality of drainage channels 34, 35, 36, 37, 38,

3.9, 40, 41 and 42 defined by the plurality of shoes 24 to 33.

A second plurality of shoes 44, 45, 46, 47, 48, 49, 50, 51, 52 and 53 cooperate with the second wire 16 such that water drains from the stock S through the second wire 16 and through a plurality of slots 54, 55, 56, 57, 58, 59, 60, 61 and 62 defined by the second plurality of shoes 44 to 53.

The first and the second plurality of shoes 24 to 33 and 44 to 53 are staggered relative to each other for enhancing the dispersion of fibers within the stock S during the formation of the web W.

More particularly, as shown in figure 1, the headbox 12 is a high consistency headbox.

The forming apparatus 10 also includes a first turning bar 64 disposed between the headbox 12 and the first end 20 of the forming section 18 such that the first wire 14 extends around the first turning bar 64.

A second turning bar 66 is disposed between the headbox 12 and the first end 20 of the forming section 18 such that the second wire 16 extends around the second turning bar 66. The jet J of stock S moves from the headbox 12 to the forming section 18 between the first and the second turning bars 64 . and 66 respectively.

In a preferred embodiment of the present invention, the turning bars are disposed at a distance not greater than 4 inches from the forming section 18.

The forming section 18 is curved in a direction from the first end 20 towards the second end 22 thereof. Therefore,- it is a primary object of the present invention to provide a forming apparatus which overcomes the inadequacies of the prior art proposals and which makes a considerable contribution to the art of forming a web from stock.

Another object of the present invention is to enhance fiber dispersion while inhibiting flocculation in high consistency forming.

Other objects and advantages provided by the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description of a preferred embodiment of the invention contained hereinafter.

SUMMARY OF THE INVENTION

The present invention relates to a forming apparatus and method for forming a web from stock. The apparatus includes a headbox for ejecting a jet of the stock. A first and a second moving wire cooperate together to define therebetween a forming section having a first and a second end. The first end is disposed closely adjacent to the headbox. A first plurality of shoes cooperate with the first wire such that water drains from the stock through the first wire and through a plurality of drainage channels defined by the first plurality of shoes.

A second plurality of shoes cooperate with the second wire such that water drains from the stock through the second wire and through a plurality of slots defined by the second plurality of shoes. The first and the second plurality of shoes are disposed in staggered relationship relative to each other for enhancing the dispersion of fibers within the stock during the formation of the web.

In a more specific embodiment of the present invention, the headbox is a high consistency headbox. Furthermore, the The curved forming section 18 is inclined upwardly from the first end 20 towards the second end thereof. The forming section subsequently descends to the second end 22 such that the stock S follows a curved path or forming section 18 from the first to the second end 20 and 22 respectively of the forming section 18. More specifically, the path 18 is an arc which has a radius R within the range 150 to 400 inches. In a specific embodiment of the present invention, the radius R is 200 inches. The curved path inhibits lateral wandering of the wires relative to the shoes.

Each shoe of the first and second plurality of shoes 24-32, 44-53 respectively is solid.

As shown in figure 2 which is an enlarged fragmentary view of the shoe 28, the shoe 28 of the first plurality of shoes 34 to 32 defines a channel 37 of the first plurality of channels 34 to 42.

The shoe 48 of the second plurality of shoes 44 to 53 defines a slot 57 of the plurality of slots 54 to 62.

The number of shoes of the first plurality of shoes 24 to 33 is equal to the number of shoes of the second plurality of shoes 44 to 53 such that the shoe 28 of the first plurality of shoes 24 to 33 is disposed in staggered relationship with the shoe 48 of the second plurality of shoes 44 to 53. The shoe 28 defines a step 68 and the shoe 48 defines a step 70.

The shoe 28 of the first plurality of shoes defines an inclined surface 72 with the inclined surface 72 being disposed in a first plane PI which converges in a machine direction indicated by the arrow MD with the first wire 14. The surface 72 extends from the channel 37 to the first wire 14.

The shoe 48 of the second plurality of shoes defines an inclined face 74. The inclined face 74 is disposed in a second plane P2 which converges in the machine direction MD with the second wire 16. The face 74 extends from the slot

57 to the second wire 16.

The forming apparatus 10 also includes means generally designated 76 for adjusting the distance between the first ^' and the second plurality of shoes for controlling the respective pressure pulses applied to the stock S during passage through the forming section 18. More particularly, the means 76 shown in figure 1 includes rails 78 and 80 and drive means (not shown) for moving an upper container 82 towards or away from a lower container 84 as indicated by the arrow 86.

A first dewatering means generally designated 88 includes a pressure vessel generally designated 90 which is connected to the channels 34 to 42.

Pressure vessel 90 is divided into at least two compartments 92, 94. Additionally, control means generally designated 96 control the flow of water through the channels 34 to 42.

More specifically, the first and a second compartment 92 and 94 of pressure vessel 90 are disposed in the machine direction MD and the control means 96 includes a first and second control valve 98 and 100 respectively for controlling the flow of water from the first and the second compartments ^"92 and 94 so that downward drainage in a machine direction MD can be controlled by use of the control valves 98 and 100.

Similarly, the upper container 82 is divided into at least two enclosures 102, 104 by a wall 106. The enclosures 102 and 104 are connected by conduits 108, 110 to a source of partial vacuum 112. Control valves 114, 116 are disposed within conduits 108, 110 for controlling the upward dewatering of the stock S through slots 54 to 62. In operation of the apparatus shown in figures 1 and 2, a high consistency stock S is ejected from the headbox 12 between converging wires 14 and 16. The wires 14 and 16 converge respectively around turning bars 64 and 66 so that a forming section 18 is formed between the wires 14 and 16.

The stock during passage through the forming section 18 is subjected to alternate upward and downward drainage through the plurality of slots and channels respectively. The degree of drainage is controlled respectively by control valves 98,

100, 114 and 116 so that a gentle dewatering of the stock is carried out while subjecting the stock to staggered pressure pulses during passage through the forming section. The distance between the upper and lower wires can be adjusted by movement of the upper container 82 on rails 78, 80 while maintaining the lower container 84 in a fixed disposition.

The present invention provides an improved means for dispersing the fibers within a high consistency stock during the formation of the web, such dispersion being attainable without undue flocculation.

Claims

What is claimed is:

1. A forming apparatus (10) for forming a web (W) from stock (S), said apparatus (10) comprising: a headbox (12) for ejecting a jet (J) of the stock (S); a first and second moving wire (14,16) cooperating together to define therebetween a forming section (18) having a first and a second end (20,22), said first end (20) being disposed closely adjacent to said headbox (12); a first plurality of shoes (24-33) cooperating with said first wire (14) such that water drains from the stock (S) through said first wire (14) and through a first plurality of channels (34-42) defined by said first plurality of shoes (24-33); a second plurality of shoes (44-53) cooperating with said second wire (16) such that water drains from the stock (S) through said second wire (16) and through a plurality of slots (54-62) defined by said second plurality of shoes (44-53); and said first and second plurality of shoes (24-33; 44-53) being staggered relative to each other for enhancing the dispersion of fibers within the stock (S) during the formation of the web (W) .

2. A forming apparatus (10) as set forth in claim 1 wherein said headbox (12) is a high consistency headbox.

3. A forming apparatus (10) as set forth in claim 1 further including: a first turning bar (64) disposed between said headbox (12) and said first end (20) of said forming section (18) such that said first wire (14) extends around said first turning bar (64); a second turning bar (66) disposed between said headbox (12) and said first end (20) of said forming section (18) such that said second wire (16) extends around said second turning bar (66), said jet (J) of stock (S) moving from said headbox (12) to said forming section (18) between said first and second turning bars (64,66).

4. A forming apparatus (10) as set forth in claim 1 wherein said forming section (18) is curved in a direction from said first (20) towards said second end (22) thereof.

^' 5. A forming apparatus (10) as set forth in claim 4 wherein said curved forming section (18) is inclined upwardly from said first end (20) towards said second end (22) thereof, said forming section (18) subsequently descending to said second end (22) thereof such that the stock (S) follows a curved path from said first (20) to said second end (22) of said forming section (18).

6. A forming apparatus (10) as set forth in claim 5 wherein said path (18) is an arc.

7. A forming apparatus (10) as set forth in claim 6 wherein said arc has a radius (R) within the range 150 to 400 inches.

8. A forming apparatus (10) as set forth in claim 1 wherein each shoe of said first and second plurality of shoes (24-32; 44-53) is solid.

9. A forming apparatus (10) as set forth in claim 8 wherein each shoe of said first plurality of shoes (24-32) defines a channel (37) of said plurality of channels (34-42).

10. A forming apparatus (10) as set forth in claim 8 wherein each shoe of said second plurality of shoes (44-53) defines a slot (57) of said plurality of slots (54-62).

11. A forming apparatus (10) as set forth in claim 1 wherein said first plurality of shoes (24-33) is equal to said second plurality of shoes (44-53) such that each shoe of said first and second plurality of shoes (24-33; 44-53) is disposed in staggered relationship, each shoe defining a step.

12. A forming apparatus (10) as set forth in claim 9 wherein each shoe (28) of said first plurality of shoes (24-33) defines an inclined surface (72), said inclined surface (72) being disposed in a first plane (PI) which converges in a machine direction (MD) with said first wire (14), said surface (72) extending from said channel (37) to said first wire (14).

13. A forming apparatus (10) as set forth in claim 10 wherein each shoe (48) of said second plurality of shoes (44-53) defines an inclined face (74), said inclined face (74) being disposed in a second plane (P2) which converges in a machine direction (MD) with said second wire (16), said face (74) extending from said slot (57) to said second wire (16).

14. A forming apparatus (10) as set forth in claim 1 further including: means (76) for adjusting the distance between said first and second plurality of shoes (24-33; 44-53) for controlling the respective pressure pulses applied to the stock (S) during passage of the stock (S) through said forming section (18).

15. A forming apparatus (10) as set forth in claim 14 wherein said means (76) includes: a pressure vessel (90) connected to said channels

(34-42); control means (96) for controlling the flow of water through said channels (34-42).

16. A forming apparatus (10) as set forth in claim 15 wherein said pressure vessel (90) includes: a first and second compartment (92,94) disposed in a machine direction (MD); said control means (96) including: a first and a second control valve (98,100) for controlling the flow of water from said first and second compartments (98,100) so that downward drainage in a machine direction (MD) can be controlled by said control valves

(98,100).

17. A forming apparatus (10) as set forth in claim 1 further including: an upper container (82), said upper container (82) defining a first and second enclosure (102,104), said enclosures (102,104) being selectively connected to a source of partial pressure (112) for controlling the upward dewatering of the stock (S).

18. A method for forming a web (W) from stock (S), said method comprising the steps of: ejecting a jet (J) of the stock (S) from a headbox (12); moving a first and a second wire (14,16) such that the wires (14,16) cooperate together to define therebetween a forming section (18) having a first and a second end (20,22), the first end (20) of the forming section (18) being disposed closely adjacent to the headbox (12); moving the first wire (14) over a first plurality of shoes (24-33) such that water drains from the stock (S) through the first wire (14) and through a first plurality of channels (34-42) defined by the first plurality of shoes (24-33); moving the second wire (16) such that the second wire (16) extends past a second plurality of shoes (44-53) so that water drains from the stock (S) through the second wire (16) and through a plurality of slots (54-62) defined by the second . plurality of shoes (44-53); and staggering the first plurality of shoes (24-33) relative to the second plurality of shoes (44-53) for enhancing the dispersion of fibers within the stock (S) during the formation of the web (W) .