TITLE; A TISSUE MAKING APPARATUS

Background of the Invention

Field of the Invention

The present invention relates to a tissue making apparatus for

making tissue from stock. More particularly, the present invention relates

to a tissue making apparatus including a Yankee dryer.

Information Disclosure Statement

Typically, during the manufacture of tissue, a web is formed by

ejecting stock from a headbox onto a forming wire of a forming section.

Subsequently the formed web is subjected to a pressing operation for

removing at least a portion of the water from the formed web.

The partially dewatered web is then guided around the heated

surface of a Yankee dryer. A Yankee dryer is essentially a rotatable

cylinder having a diameter of approximately 25 foot. The cylinder is

connected internally with a source of super-heated steam so that as the web is guided about the peripheral surface of the heated cylinder, the web is dried.

Subsequently, the dried web is doctored from the surface of the

cylinder and is then wound onto a reel. In order to assist in the drying of

the web during passage thereof around the Yankee dryer, air caps enclose

at least a portion of the peripheral surface of the cylinder. Hot air is

directed from such air caps onto the surface of the web in order to improve

the web drying process.

By the provision of a through-drying means, which includes blowing

high temperature air through the formed web, the present invention

eliminates the need for a costlypress section for initially dewatering the

web.

Not only does the elimination of the press section greatly decrease the overall cost of the installation of a tissue making apparatus, but also

the aforementioned through-drying, or air impingement arrangement,

according to the present invention, greatly increases the speed at which

tissue can be manufactured.

Additionally, by the provision of the aforementioned air drying means, the diameter of the subsequent Yankee dryer can be much less

than that of the typically installed Yankee dryer. Such reduction in

diameter not only reduces the overall height of the resultant tissue making

apparatus, but also avoids the inherent problems encountered during

transportation of the prior art large diameter Yankee dryers to an

installation site.

Therefore, it is a primary objective of the present invention to

overcome the aforementioned inadequacies of the prior art tissue making

machines and to provide a tissue making apparatus which makes a

significant and non-obvious contribution to the art of making tissue.

An objective of the present invention is the provision of a tissue

making apparatus which is able to operate at a substantially higher speed

when compared with currently available tissue making machines.

Another object of the present invention is the provision of a tissue

making apparatus which avoids the need for the provision of a pressing

section.

SUBSTITUTE SHEET

Another object of the present invention is the provision of a tissue

making apparatus in which the Yankee dryer has a diameter which is

substantially less than the diameter of Yankee dryers installed in prior art

machines.

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 tissue making apparatus and

method for making tissue from stock. The apparatus includes a former for

forming a web of wet tissue from the stock. Air drying means are disposed

immediately downstream relative to the former for drying the web of wet

tissue. A Yankee dryer is disposed downstream relative to the drying

means for completing the drying of the tissue.

In a more specific embodiment of the present invention/the former

includes a first and a second looped forming wire which cooperate together

to define therebetween a forming section having a first and a second end.

A headbox isdisposed closely adjacent to the first end of the forming

section for ejecting the stock into the forming section through the first end

thereof.

The former also includes a forming roll which cooperates with the

second wire such that the second wire is disposed between the first wire

and the forming roll during passage of the second wire through the forming

section. The forming roll preferably is an open roll.

The headbox includes a plurality of trailing elements for damping

turbulence of the stock during passage thereof through the headbox.

The tissue making apparatus also includes transfer means for

transferring the web of wet tissue from the second forming wire to the air

drying means.

More specifically, the transfer means includes a looped transfer felt

and a plurality of guide rolls which are disposed within the looped transfer

felt for guiding the transfer felt. The plurality of guide rolls include a

suction roll, which is disposed closely adjacent to the second forming wire

such that the transfer felt is disposed between the second forming wire

and the suction roll. The arrangement is such that when the suction roll is

connected to a source of partial vacuum, the web of wet tissue is

transferred from the second forming wire onto the transfer felt. A

downstream guide roll is disposed closely adjacent to the air drying means

such that the web of wet tissue is disposed between the transfer felt and

the air drying means so that the web of wet tissue is transferred from the

transfer felt to the air drying means.

The air drying means includes a looped dryer felt for supporting the

web of wet tissue between the former and the Yankee dryer. A plurality of

support rolls are disposed within the looped dryer felt for supporting the

dryer felt. The support rolls are disposed such that the dryer felt defines an

upwardly bowed surface for the transport thereon of the web of wet

tissue. Hot air impingement means cooperate with the bowed surface such

that the web of wet tissue supported by the dryer felt is disposed between

the bowed surface and the air impingement means. The arrangement is

such that when the air impingement means is connected to a source of

high pressure heated air, such air is blown onto the web of wet tissue and

through the dryer felt for drying the web of tissue.

Additionally, the air drying means includes vacuum means disposed

adjacent to the bowed surface. The vacuum means is disposed on an

opposite side of the dryer felt relative to the air impingement means such

that when the vacuum means is connected to a source of partial vacuum, a

flow of heated air from the air impingement means through the web of wet tissue and through the dryer felt is enhanced.

The looped dryer felt is fabricated from materials which are capable of withstanding high temperatures. Also/the hot air impingement means is

disposed above the bowed surface, and the air drying means includes lifting

means connected to the air impingement means for lifting the air

impingement means away from the bowed surface in order to facilitate

removal of broke therefrom in the event of a web breakage.

In a specific embodiment of the present invention, the source of high

pressure heated air supplies air at a temperature within the range 500° to

800° Fahrenheit, and more particularly, approximately 700° Fahrenheit, so

that the web attains a dryness within the range 45 to 90 percent dry,

dependent upon the type of furnish being dried, such dryness being

attained during passage of the web through the air drying means.

More specifically, the air drying means dries the web of wet tissue

from a solids level within the range 25 to 35 percent dry to a solids level

within the range 45 to 90 percent dry during passage of the web of wet

tissue through the air drying means.

The source of partial vacuum connected to the vacuum means is at a

vacuum level within the range .5 to 2 inches water column (WC).

In an alternative embodiment of the present invention, the transfer

means includes a suction means which cooperates with the second wire for

picking up the web of wet tissue from the second wire. The suction means cooperates with the air drying means for transferring the web of wet tissue

directly onto the air drying means.

The air drying means also includes a pick-up roll which is disposed

closely adjacent to the suction means so that the web of wet tissue is

disposed between the suction means and the pick-up roll so that when the

pick-up roll is connected to a source of partial vacuum, the web of wet

tissue is drawn away from the suction means onto the looped dryer felt, which is disposed between the web of wet tissue and the pick-up roll.

The tissue making apparatus also includes a transfer belt for

transferring the web from the air drying means to the Yankee dryer.

The Yankee dryer includes a rotatable cylinder which is connected

internally to a source of pressurized steam for completing the drying of the

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web of tissue. Air cap means cooperate with the cylinder, the air cap

means being connected to a source of pressurized heated air such that the

pressurized heated air flows from the air cap meanstowards the web of

tissue supported by and extending around the cylinder. The arrangement is

such that the web of tissue is heated on one side thereof through direct

surface contact of the web of tissue supported by the cylinder. The other

side of the web is also heated by the pressurized heated air flowing from

the air cap means towards the web of tissue during movement thereof

around the cylinder.

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 contained hereinafter, taken in conjunction with the annexed

drawings.

However, such variations and modifications 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 tissue making apparatus

according to the present invention;

SUBSTITUTE SHEET

Figure 2 is an enlarged view of the former shown in Figure 1 ;

Figure 3 is an enlarged view of a transfer means shown in Figure 1 ;

Figure 4 is an enlarged view of an air drying means shown in Figure 1 and

Figure 5 is a side-elevational view similar to that shown in Figure 1

but showing an alternative embodiment of the present invention in which

the web is transferred directly from the forming section onto a drying means without the need of a transfer felt;

Figure 6 is an enlarged view of Figure 5 showing the alternative

transfer means for transferring the web from the former to a drying means;

Figure 7 is an enlarged view of the Yankee dryer shown in Figure 1.

Similar reference numerals 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 tissue making apparatus,

generally designated 10, for making tissue T from stock S. The apparatus

10 includes a former, generally designated 12, for forming a web of wet

tissue W from the stock S.

Air drying means, generally designated 14, are disposed immediately

downstream relative to the former 12 without the interposition

therebetween of a press section. The air drying means 14 dries the web of

wet tissue W.

A Yankee dryer, generally designated 16, is disposed downstream

relative to the drying means 14 for completing the drying of the tissue W.

Figure 2 is an enlarged view of the former 12 shown in Figure 1 .

The former 12 includes a first and second looped forming wire 18 and 20,

respectively, which cooperate together to define therebetween a forming

section 22 having a first and a second end 24 and 26, respectively.

A headbox, generally designated 28, is disposed closely adjacent to

the first end 24 of the forming section 22 for ejecting the stock S into the

forming section 22 through the first end 24 thereof.

SUBSTITUTE SHEET

The former 12 further includes a forming roll 30 which cooperates

with the second wire 20 such that the second wire 20 is disposed between

the first wire 18 and the forming roll 30 during passage of the second wire

20 through the forming section 22. As shown in Figure 2, the forming roll

30 is an open roll.

The headbox 28 includes a plurality of trailing elements 32,33,34 for

damping turbulence of the stock S during passage thereof through the

headbox 28.

Figure 3 is an enlarged view of a transfer means, generally

designated 36, shown in Figure 1 . The transfer means 36 transfers the

web of wet tissue W, as indicated by the dashed line, from the second

forming wire 20 to the air drying means 14.

More specifically, the transfer means 36 includes a looped transfer

felt 38 and a plurality of guide rolls 40, 41 ,42 and 43 which are disposed

within the looped transfer felt 38 for guiding the transfer felt 38.

The plurality of guide rolls 40 to 43 include a suction roll 40 which is

disposed closely adjacent to the second forming wire 20 such that the

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transfer felt 38 is disposed between the second forming wire 20 and the

suction roll 40 so that when the suction roll 40 is connected to a source of

partial vacuum 44, the web of wet tissue W is transferred from the second

forming wire 20 onto the transfer felt 38.

A downstream guide roll 41 is disposed closely adjacent to the air

drying means 14 such that the web of wet tissue W is disposed between the transfer felt 38 and the air drying means 14 so that the web of wet

tissue W is transferred from the transfer felt 38 to the air drying means 14.

Figure 4 is an enlarged view of the air drying means 14 shown in

Figure 1 . The air drying means 14 includes a looped dryer felt 46 for

supporting the web of wet tissue W between the former 12 and the

Yankee dryer 16. A plurality of support rolls 48, 49, 50, 51, 52, 53, 54,

55, 56, 57, 58, 59, 60, 61 , 62, 63, 64, 65, 66, 67, 68 ,69 are disposed

within the looped dryer felt 46 for supporting the dryer felt 46. The support rolls 48 to 69 are disposed such that the dryer felt 46 defines an

upwardly bowed surface 70 for the transport thereon of the web of wet

tissue W.

Air impingement means, generally designated 72, cooperate with the

bowed surface 70 such that the web of wet tissue W supported by the

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dryer felt 46 is disposed between the air impingement means 72. The

arrangement is such that when the air impingement means 72 is connected

to a source of high pressure heated air 74, such air, as indicated by the

arrow 76,77,78, is blown onto the web of wet tissue W and through the

dryer felt 46 for drying the web of tissue W.

Additionally, as shown in Figure 4, the air drying means 14 includes

vacuum means, generally designated 80, disposed adjacent to the bowed

surface 70. The vacuum means 80 is disposed on an opposite side of the

dryer felt 46 relative to the air impingement means 72 such that when the

vacuum means 80 is connected to a source of partial vacuum 82, the flow

of heated air 76-78 from the air impingement means 72 through the web of

wet tissue W and through the dryer felt 46 is enhanced.

The vacuum means 80 includes a box-like arrangement which

encloses most of the surface of the support rolls. The vacuum box

includes cross-machine directional slots for the protrusion therethrough of

at least a portion of the peripheral surface of the support rolls for assisting

in the support of the dryer felt. The box also includes a plurality of orifices

which permit the through-flow of air from the hot air impingement means

72 through the web W and into the vacuum means 80.

SUR55T-!7-l*T~ f^HΞ ^

The looped dryer felt 46 is fabricated from materials which are

capable of withstanding high temperatures.

The hot air impingement means is disposed above the bowed surface

70, and the air drying means 14 further includes lifting means, generally

designated 84, which is connected to the air impingement means 72 for

lifting the air impingement means 72 away from the bowed surface 70 in

order to facilitate removal of broke therefrom in the event of a web

breakage.

The source of high pressure heated air 74 supplies pressurized air

76-78 at a temperature within the range 500° to 800° Fahrenheit so that

the web attains a dryness within the range 45 to 90 percent dry during

passage of the web through the air drying means 14.

More specifically, the air drying means 14 dries the web of wet

tissue W from a solids level within the range 25 to 35 percent dry to a

solids level within the range 45 to 90 percent dry during passage of the

web of wet tissue W through the air drying means 14.

The source of partial vacuum 82 connected to the vacuum means 80

is at a vacuum level within the range .5 to 2 inches water column (WC).

SUBSTITUTE SHEE

Figure 5 shows an alternative embodiment of the present invention in

which a transfer means, generally designated 36A, transfers the web WA

directly from a second wire 20A of a former 12A onto a dryer felt 46A of

an air drying means 14A.

Figure 6 is an enlarged view of the transfer means 36A shown in

Figure 5. The transfer means 36A includes a suction means 40A which

cooperates with the second wire 20A for picking up the web of wet tissue

WA from the second wire 20A. The suction means 40A cooperates with

the air drying means 14A for transferring the web of wet tissue WA

directly onto the air drying means 14A.

More specifically, the air drying means 14A includes a looped dryer

felt 46A for supporting the web of wet tissue WA between the former 12A

and a Yankee dryer 16A. A plurality of support rolls are disposed within

the looped dryer felt 46A for supporting the dryer felt 46A, the support

rolls being disposed such that the dryer felt 46A defines an upwardly

bowed surface 70A for the transport thereon of the web of wet tissue WA.

The plurality of support rolls include a pick-up roll 86 which is

disposed closely adjacent to the suction means 40A so that the web of wet

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tissue WA is disposed between the suction means 40A and the pick-up roll

86 so that when the pick-up roll 86 is connected to a source of partial vacuum 88, the web of wet tissue WA is drawn away from the suction

means 40A onto the looped dryer felt 46A, which is disposed between the

web of wet tissue WA and the pick-up roll 86.

Figure 7 shows a transfer belt 90 for transferring the web W from

the air drying means 14 to the Yankee dryer 16.

As shown in Figure 7, the Yankee dryer 16 includes a rotatable cylinder 92 which is connected internally to a source of pressurized steam

94 for completing the drying of the web of tissue W.

Air cap means, generally designated 96, cooperate with the cylinder

92. The air cap means 96 are connected to a source of pressurized heated air 98 such that the pressurized heated air flows, as indicated by the arrow

100, from the air cap means 96 towards the web of tissue W supported by

and extending around the cylinder 92. The arrangement is such that the

web of tissue W is heated on one side thereof through direct surface

contact of the web of tissue W supported by the cylinder 92, while the

other side of the web is heated by the pressurized heated air 100 flowing

SUBSTITUTE SHEET

from the air cap means 96 towards the web of tissue during movement

thereof around the cylinder 92.

In operation of the apparatus, the method includes the steps of: 1 )

ejecting the stock onto a forming wire of a former; 2) transferring the

formed web of wet tissue onto a drying felt supported by a plurality of rolls

such that the dryer felt defines an upwardly bowed surface, the web of

wet tissue being transferred immediately from the former to the dryer felt

without the interposition therebetween of a pressing operation; 3) blowing

hot air through the web supported on the bowed surface so that the web

attains a dryness of up to 90 percent bone dry; and 4) transferring the web

from the dryer felt to a Yankee dryer for completing the drying of the web,

such Yankee dryer completing the drying of the web without the flow of air

through the cylindrical wall of the Yankee dryer, the arrangement enabling

the more efficient utilization of thermal energy than a through-air dryer.

The present invention greatly increases the speed at which tissue

can be manufactured because the web is progressively dried during

movement thereof over the bowed surface of the drying means without any

need for the web to change directions, as has been the case with some

prior art tissue machines provided with a serpentine type dryer arrangement

prior to the Yankee dryer.

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Also, due to the efficiency of the air drying means, the Yankee dryer may have a minimal diameter and yet efficiently complete the drying

operation.

Also, the present invention avoids the need for the provision of a

costly press section.

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