EP0723613B1

EP0723613B1 - A forming apparatus for forming a web from stock

Info

Publication number: EP0723613B1
Application number: EP94927335A
Authority: EP
Inventors: James Arthur Turner
Original assignee: Beloit Technologies Inc
Current assignee: Beloit Technologies Inc
Priority date: 1993-10-16
Filing date: 1994-08-31
Publication date: 1998-12-16
Anticipated expiration: 2014-08-31
Also published as: EP0723613A1; DE69415338D1; CA2174228A1; GB9321401D0; DE69415338T2; JP2686853B2; PL313915A1; BR9407827A; FI961654A0; FI961654A; CN1039931C; KR960705108A; WO1995011338A1; CN1133077A; JPH08512367A

Description

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 apparatus relates to a twin-wire forming apparatus.

Information Disclosure Statement

Twin wire formers, such as the BEL BOND® former, have greatly increased the quality of the web formed thereby. BEL BOND is a registered trademark of Beloit Corporation.

More particularly, when stock is ejected onto a horizontally moving fourdrinier wire, water within the stock flows downwardly from the stock through the fourdrinier wire, leaving a partially dewatered web on the top surface of the fourdrinier wire.

However, such downward removal of water tends to generate a resultant web having different surface characteristics thereon due to the one-sided removal of water therefrom during formation.

The aforementioned BEL BOND® former was designed typically as a retrofit top wire unit which permitted upward removal of water from the partially dewatered web. Such upward removal of water is attained by means of an auto-slice or vacuum slot disposed within the loop of the upper forming wire.

Additionally, such upward removal of water through the top wire is due to the provision of curved shoe for guiding the fourdrinier wire such that water is removed centrifugally and upwardly from the stock through the top wire.

A typical example of such a web former is disclosed in WO-A-91 13206 which describes a forming apparatus according to the preamble of claim 1.

The following documents are also representative of the art of paper forming apparatus:

WO-A-89 04397 describes a forming apparatus which includes pressure chambers and a band within the lower wire loop for aiding in dewatering the web suspension upwardly.

EP-A-0 389 404 describes a multi-ply paper forming apparatus which includes a curved inverted vacuum box in the upper wire loop to permit upward removal of water from the web.

In EP-A-0 122 701, a curved inverted vacuum box is also disposed in the upper wire loop, the arrangement being such that suction and pressure is applied to the fibrous suspension for dewatering it.

However, with the advent of recycled paper and various board grades, problems have been experienced in removing sufficient quantities of water from the stock.

The present invention overcomes the aforementioned problem by the provision of a movable blanket disposed beneath a curved inverted vacuum box for pressing the wires against a curved face of the aforementioned curved inverted vacuum box for gently removing therefrom further quantities of water.

Therefore, it is a primary objective of the present invention to provide a forming apparatus which overcomes the aforementioned inadequacies of the prior art machines and which makes a considerable contribution to the art of removing water from stock.

Another object of the present invention is the provision of a twin-wire forming apparatus which includes a looped blanket which cooperates with a fourdrinier wire for urging the fourdrinier wire against a curved face of a curved inverted vacuum box for removing water from stock disposed between the wires moving between the blanket and the curved face.

To achieve this, the forming apparatus of the invention comprises the features claimed in the characterizing part of claim 1.

Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter, taken in conjunction with the annexed drawings.

Summary Of The Invention

The present invention relates to a forming apparatus for forming a web from stock ejected from a headbox. The apparatus includes a fourdrinier wire which defines a substantially horizontal section having a first and a second end.

A headbox is disposed adjacent to and above the first end of the section for ejecting the stock onto the fourdrinier wire between the first and the second end of the section.

A looped forming wire cooperates with and is disposed above the horizontal section such that the fourdrinier wire and the forming wire define therebetween an elongate forming section for removing water from the stock. The forming section has an upstream and a downstream end.

A curved forming shoe is disposed adjacent to the upstream end of the forming section and on an opposite side of the fourdrinier wire relative to the headbox. The arrangement is such that during movement of the fourdrinier wire over the curved shoe, water is thrown centrifugally from the stock upwardly through the forming wire.

A vacuum slot is disposed on an opposite side of the wires relative to the shoe for conveying the water removed centrifugally through the forming wire.

A curved inverted vacuum box is disposed immediately downstream relative to the vacuum slot and on the same side of the wires as the vacuum slot.

The curved vacuum box defines a curved face for guiding the wires. The curved face is curved in an opposite sense relative to the curved forming shoe.

A looped blanket means is disposed on the same side of the wires as the shoe. The blanket means is disposed adjacent to and on the opposite side of the wires relative to the curved face. The blanket means cooperates with the fourdrinier wire for pressing the fourdrinier wire against the curved face for urging a further portion of water away from the formed web upwardly through the forming wire.

In a more specific embodiment of the present invention, the fourdrinier wire defines an upstream section immediately ahead of the horizontal section. The horizontal section is dipped relative to the upstream section such that the ejection of stock onto the horizontal section is at a relatively small angle relative to the horizontal section for minimizing bouncing of the stock on the horizontal section. The stock is ejected onto the horizontal section upstream relative to the curved shoe.

Furthermore, the upstream end of the forming section includes means for adjusting a wrap of the forming wire around the curved shoe for adjusting the flow of water through the forming wire.

The forming shoe includes a plurality of blades, with each blade extending in a cross-machine direction. The blades are spaced relative to each other in a machine direction.

The vacuum slot includes an adjustable guide for guiding the water removed centrifugally from the stock through the forming wire. The slot is connected to a source of partial vacuum for assisting removal of the water.

The curved face includes a plurality of foils, with each foil extending in a cross-machine direction. The foils are spaced relative to each other in a machine direction for guiding the forming wire.

Additionally, the curved face includes a first zone and a second zone disposed downstream relative to the first zone. The second zone has a radius of curvature which is less than the radius of curvature of the first zone.

The second zone is disposed immediately downstream relative to the first zone, with the second zone having a downstream extremity.

The downstream extremity, the second end of the horizontal section and the downstream end of the forming section are all disposed adjacent to each other.

The blanket means in one embodiment of the present invention is a non-porous blanket which defines a smooth surface which cooperates with the fourdrinier wire.

In another embodiment of the present invention, the blanket means is a vented blanket for assisting removal of water pressed from the stock during movement of the stock between the wires between the blanket means and the curved face.

The forming apparatus also includes stretching means for stretching the blanket means such that the blanket means is urged upwardly against the fourdrinier wire.

Many modifications and variations of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description, taken in conjunction with the annexed drawings.

However, such modifications and variations fall within the 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;

Figure 2 is an enlarged view of a portion of the blanket means showing the blanket means having a smooth non-porous surface; and

Figure 3 is a similar view to that shown in Figure 2, but shows an alternative embodiment of the present invention in which the blanket means is vented.

Similar reference characters refer to similar parts throughout the various embodiments of the present invention.

Detailed Description Of The Drawings

Figure 1 is a side-elevational view of a forming apparatus, generally designated 10 according to the present invention, for forming a web W from stock S ejected from a headbox 12. The apparatus 10 includes a fourdrinier wire 14 defining a substantially horizontal section 16 having a first and a

second end

18 and 20, respectively.

The headbox 12 is disposed adjacent to and above the first end 18 of the section 16 for ejecting the stock S onto the fourdrinier wire 14 between the first and the

second end

18 and 20 of the section 16.

A looped forming wire 22 cooperates with and is disposed above the horizontal section 16 such that the fourdrinier wire 14 and the forming wire 22 define therebetween an elongate forming section 24 for removing water from the stock S. The forming section 24 has an upstream and a

downstream end

26 and 28, respectively.

A curved forming shoe 30 is disposed adjacent to the upstream end 26 of the forming section 24 and on an opposite side of the fourdrinier wire 14 relative to the headbox 12. The arrangement is such that during movement of the fourdrinier wire 14 over the curved shoe 30, water, as indicated by the arrow 32, is thrown centrifugally from the stock S through the forming wire 22.

A vacuum slot 34 is disposed on an opposite side of the

wires

14 and 22 relative to the shoe 30 for conveying the water 32 removed centrifugally through the forming wire 22.

A curved inverted vacuum box 36 is disposed immediately downstream relative to the vacuum slot 34 and on the same side of the

wires

14 and 22 as the vacuum slot 34.

The curved vacuum box 36 defines a curved face 38 for guiding the

wires

14 and 22. The curved face 38 has a curvature in an opposite sense relative to the curved forming shoe 30.

A looped blanket means 40 is disposed on the same side of the

wires

14 and 22 as the shoe 30. The blanket means 40 is disposed adjacent to and on the opposite side of the

wires

14 and 22 relative to the curved face 38. The blanket means 40 cooperates with the fourdrinier wire 14 for pressing the fourdrinier wire 14 against the curved face 38 for urging a further portion of water, as indicated by the arrow 42, away from the formed web W and through the forming wire 22.

As shown in Figure 1, the fourdrinier wire 14 also defines an upstream section 44 immediately ahead of the horizontal section 16. The horizontal section 16 is dipped relative to the upstream section 44 such that when the stock S is ejected onto the horizontal section 16, the trajectory of the stock is at a relatively small angle relative to the horizontal section 16. By this means, bouncing of the stock S on the horizontal section 16 is minimized, and the stock S is ejected onto the horizontal section 16 upstream relative to the curved shoe 30.

The upstream end 26 of the forming section 24 also includes means 46 for adjusting a wrap of the forming wire 22 around the curved shoe 30 for adjusting the flow of water 32 through the forming wire 22.

The forming shoe 30 also includes a plurality of

blades

48,49 and 50. Each blade, for example blade 48, extends in a cross-machine direction. The blades 48 to 50 are spaced relative to each other in a machine direction MD.

The vacuum slot 34 includes an adjustable guide 52 for guiding the water 32 removed centrifugally from the stock S through the forming wire 22. The slot 34 is connected to a source of partial vacuum for assisting removal of the water 32.

The curved face 38 includes a plurality of

foils

54,55 and 56. Each of the foils 54 to 56 extends in a cross-machine direction. The foils 54 to 56 are spaced relative to each other in a machine direction MD for guiding the forming wire 22.

The curved face 38 includes a first zone 58 and a second zone 60 which is disposed downstream relative to the first zone 58. The second zone 60 has a radius of curvature which is less than a radius of curvature of the first zone 58. In a specific embodiment of the present invention, the first zone has a radius of curvature of approximately 5 meters.

The second zone 60 is disposed immediately downstream relative to the first zone 58. The second zone 60 has a downstream extremity 62.

The downstream extremity 62 and the downstream end 28 of the forming section 24 are disposed adjacent to each other.

In one embodiment of the present invention as shown in Figure 2, the blanket means 40 is a non-porous blanket 64 which defines a smooth surface 66 which cooperates with the fourdrinier wire 14.

In an alternative embodiment of the present invention as shown in Figure 3, a blanket means 40A is a vented blanket 64A for assisting removal of water pressed from the stock S during movement of the stock S between the

wires

14 and 22 between the blanket means 40A and the curved face 38.

More specifically, the vented blanket 64A is a grooved blanket with

grooves

66 and 67.

Furthermore, as shown in Figure 1, the forming apparatus 10 further includes stretching means 68 for stretching the blanket means 40 such that the blanket means 40 is urged upwardly, as indicated by the arrow 70, against the fourdrinier wire 14.

In operation of the apparatus according to the present invention, stock is ejected from the headbox 12 onto the fourdrinier wire. The stock is conveyed by the fourdrinier wire 14 such that the partially formed web is disposed between the

wires

14 and 22.

Water is removed upwardly through the wire 22 and downwardly through the shoe 30 during movement thereof past the curved shoe.

Further water is removed upwardly through the curved inverted vacuum box 36.

Upward removal of the further quantity of water is assisted by the provision of the blanket means 40 which urges the fourdrinier wire 14 upwardly so that the web is squeezed between the wires during movement thereof past the curved face 38.

The present invention permits drainage of water from board grades manufactured particularly from waste furnish by the provision of a gentle pressing of the water from the formed web during the forming operation.

Claims

A forming apparatus (10) for forming a web (W) from stock (S) ejected from a headbox (12), said apparatus comprising:

a fourdrinier wire (14) defining a substantially horizontal section (16) having a first and a second end (18,20),

a headbox (12) disposed adjacent to and above said first end (18) of said section (16) for ejecting the stock (S) onto said fourdrinier wire (14) between said first and said second end (18,20) of said section (16),

a looped forming wire (22) cooperating with and disposed above said substantially horizontal section (16) such that said fourdrinier wire (14) and said forming wire (22) define therebetween an elongate forming section (24) for removing water from the stock (S), said forming section (24) having an upstream and a downstream end (26, 28),

a curved forming shoe (30) disposed adjacent to said upstream end (26) of said forming section (24) and on an opposite side of said fourdrinier wire (14) relative to said headbox (12), the arrangement being such that during movement of said fourdrinier wire (14) over said curved shoe (30), water (32) is thrown centrifugally from the stock (S) through said looped forming wire (22),

a vacuum slot (34) disposed on an opposite side of said wires (14,22) relative to said shoe (30) for conveying said water (32) removed centrifugally through said looped forming wire (22),

a curved inverted vacuum box (36) disposed immediately downstream relative to said vacuum slot (34) and on the same side of said wires (14,22) as said vacuum slot (34), said vacuum box (36) being disposed within said looped forming wire (22),

said curved vacuum box (36) defining a curved face (38) for guiding said wires (14,22), said curved face contacting said forming wire (22) and slidingly supporting said forming wire, said curved face (38) being curved in an opposite sense relative to said curved forming shoe (30),

characterized in further comprising a looped blanket means (40) disposed on the same side of said wires (14,22) as said shoe (30), said blanket means (40) being disposed adjacent to and on the opposite side of said wires (14,22) relative to said curved face (38), and
stretching means (68) for stretching said blanket means (40) such that said blanket means (40) is urged upwardly (70) against said fourdrinier wire (14), whereby said blanket means (40) cooperates with said fourdrinier wire (14) for pressing said fourdrinier wire (14) upwardly towards said curved face (38) for urging a further portion of water (42) away from the formed web (W) and through said forming wire (22).
A forming apparatus as set forth in claim 1, characterized in that said fourdrinier wire (14) defines an upstream section (44) disposed immediately ahead of said substantially horizontal section (16), said substantially horizontal section (16) being dipped relative to said upstream section (44) such that said ejection of stock (S) onto said substantially horizontal section (16) is at a relatively small angle relative to said substantially horizontal section (16) for minimizing bouncing of the stock (S) on said substantially horizontal section (16), said stock (S) being ejected onto said substantially horizontal section (16) upstream relative to said curved shoe (30).
A forming apparatus as set forth in claim 1, characterized in that said upstream end of said forming section (24) includes:

means (46) for adjusting a wrap of said forming wire (22) around said curved shoe (30) for adjusting the flow of water (32) through said forming wire (22).
A forming apparatus as set forth in claim 1, characterized in that said forming shoe (30) includes:

a plurality of blades (48, 49, 50), each blade extending in a cross-machine direction, said blades (48, 49, 50) being spaced relative to each other in a machine direction (MD).
A forming apparatus as set forth in claim 1, characterized in that said vacuum slot (34) includes:
an adjustable guide (52) for guiding said water (32) removed centrifugally from the stock (S) through said forming wire (22), said slot (34) being connected to a source of partial vacuum for assisting removal of said water (32).
A forming apparatus as set forth in claim 1, characterized in that said curved face (38) includes:

a plurality of foils (54,55,56), each foil (54,55,56) extending in a cross-machine direction, said foils (54,55,56) being spaced relative to each other in a machine direction (MD) for guiding said forming wire (22).
A forming apparatus as set forth in claim 1, characterized in that said curved face (38) includes:

a first zone (58);

a second zone (60) disposed downstream relative to said first zone (58), said second zone (60) having a radius of curvature which is less than a radius of curvature of said first zone (58).
A forming apparatus as set forth in claim 7, characterized in that said second zone (60) is disposed immediately downstream relative to said first zone (58), said second zone (60) having a downstream extremity (62).
A forming apparatus as set forth in claim 8, characterized in that said downstream extremity (62), said second end (20) of said substantially horizontal section (16) and said downstream end (28) of said forming section (24) are disposed adjacent to each other.
A forming apparatus as set forth in claim 1, characterized in that said blanket means (40) is a non-porous blanket (64) which defines a smooth surface (66) which cooperates with said fourdrinier wire (14).
A forming apparatus as set forth in claim 1, characterized in that said blanket means (40A) is a vented blanket (64A) for assisting removal of water pressed from the stock (S) during movement of the stock (S) between said wires (14,22) between said blanket means (40A) and said curved face (38).