GB2071293A

GB2071293A - Dewatering press

Info

Publication number: GB2071293A
Application number: GB8104283A
Authority: GB
Original assignee: Albany International Corp
Current assignee: Albany International Corp
Priority date: 1980-03-07
Filing date: 1981-02-11
Publication date: 1981-09-16
Also published as: NZ196403A; IT8147953A0; AU6747981A; BE887821A; AU539576B2; ZA81676B; CA1173283A; FR2477596A1; BR8101271A; DE3105615A1; JPS56165091A; GB2071293B; NL8100500A

Abstract

A method and apparatus for dewatering fabrics such as wet paper are disclosed. The apparatus includes a pair of press rollers (14, 16) through which a wet paper web (10) is passed. A pair of endless contact felts (22) made from cotton or other cellulosic fibres are passed between the rollers to absorb liquid from the web. To provide cushion in the nip and reduce the wear of the contact felts, a pair of endless inner felts (18) pass between the rollers and the contact felts. The inner felts may be made from nylon. <IMAGE>

Description

SPECIFICATION Dewatering press The field of the invention relates to a method and apparatus for dewatering fabrics, and particularly to the use of a dewatering press.

Press sections and wet felts have been used in the paper industry for reducing the moisture content of wet paper webs. A web is caused to pass between a pair of rollers which squeeze- it to a limited extent to facilitate the extraction process.

The web is typically carried by an endless felt through the press rolls. The felt absorbs water from the web, and the water is subsequently removed by appropriate means positioned along the path travelled by the felt. Suction assemblies and blowers have been employed for drying felts.

Dewatering presses have been disclosed in U.S.

Patent Nos. 3,093,535; 3,214,329; 3,214,330; 3,214,331; 3,257,268; 3,278,368; 3,325,351; 3,556,940; and 3,840,429. Some employ more than one endless felt four conveying paper webs through press nips.

The invention is directed to a novel arrangement for removing water from a paper web.

It is an object of the invention to remove water from a web through the use of press rollers and a felt while avoiding rewetting the web at any point.

It is another object of the invention to provide a dewatering press assembly which can be used after a conventional press assembly for drying a web to an extent which conventional assemblies cannot.

These and other objects are attained through the use of a dewatering press including at least two endless felts, the felt in contact with the web having properties which allow it to hold water and a backup felt able to give cushion in the nip. The contact felt is preferably made from cotton or cellulosic fibre as it will attract and hold water pressed from a wet paper web. Rewetting of the web is accordingly prevented. The backup felt may be made from-100% nylon which is woven and needled using nylon web.

The invention is both efficient in its removal of water and economical. If the contact web wears out due to its relatively fragile fibres, it may simply be replaced. It would be uneconomical to needle cotton or other cellulosic fibres into the face of a conventional press felt as the entire fabric would have to be replaced when the fibres wear out. The individual use of a cotton felt would also be short lived due to excessive wear. The provision of a contact felt to remove moisture and an inner nylon fabric to provide cushion and reduce wear is a most satisfactory solution. The inner felt contacts the press roller while overlapped by the contact felt in the vicinity of the nip.

By way of example an embodiment of the invention will now be described with reference to the drawing which shows a dewatering assembly of the type intended for use in a paper making machine.

A liquid-containing paper web 10 is shown passing through one of the press sections 12 of the machine. As is known in the art, one or more such sections 12 may be present in the machine.

The press section 12 includes a pair of rollers 14, 1 6 positioned one above the other.

A pair of endless inner felts 1 8 are positioned about each of the press rollers 14, 1 6 and about a plurality of guide rolls 20. The inner felts 18 are composed of a material which is both durable and able to provide cushioning in the nip. A 100% nylon felt which is woven and needled using nylon web and which is compacted to a high density has been found to be suitable for the intended purpose.

A pair of endless contact felts 22 are arranged upon guide rolls 20 to pass between the rollers 14, 1 6. The web 10 passes between and is contacted by the contact felts. When the web is passed through the nip of the press section 12, water is pressed therefrom into the contact felts at the point where it enters between the rolls. As the web emerges from the nip, there is danger that some of the expressed liquid will return to the web. This is known as rewetting.

Conventional sections are used to reduce the wetness of the web to about 60%. Due to the rewetting problem, there is a point where additional conventional presses do not further .reduce the moisture content. It has been found that fabrics made from cotton or other cellulosic fibres are effective against the rewet problem. The contact felts 22 are woven from a yarn of such fibres. The back-up felts 18 are used in the combination to provide longer life and reduction of wear. This allows the assembly shown in the drawing to be used in conjunction with conventional press sections. The press shown in the drawing is effective against rewetting and can be used after conventional presses to reduce the wetness of the web to about the 45% level.

After emerging from the press sections, the web proceeds to steam operated drying means (not shown) for further reducing'the moisture content. It will be appreciated that substantial steam costs can be saved by using a press as disclosed. Savings in steam costs to dry paper may exceed 50%.

In operation, the felts proceeding about the upper press roller 14 travel in a counter-clockwise direction while those moving about the lower roller travel clockwise. A moisture-containing paper web, which may have been previously treated by a conventional dewatering press, enters the nip between the rollers 14, 1 6. Liquid is accordingly expressed therefrom. When the web emerges from the nip, the cotton contact felts, which have absorbed moisture from both sides of the web, prevent significant rewetting.

Substantial reductions in moisture content are accordingly obtained. The paper web proceeds from the nip to undergo further processing.

The felts pass about the guide rolls 20 and through conditioning means 24. The conditioning means are known to the art and may be adapted to remove liquid and other materiais from the felts.

Those skilled in the art will appreciate that modifications can be made in the structure disclosed without departing from the spirit of the invention. The scope of the invention should accordingly be determined by reference to the appended claims.

Claims

1. A dewatering press for drying fabrics such as moisture-containing paper webs, comprising: a first press roller; a second press roller positioned adjacent to said first press roller and forming a nip between said rollers; a first endless felt positioned about and contacting said first press roller; and a second endless felt positioned about said first endless felt and about said first press roller, said second endless felt overlapping and contacting said first endless felt in the area of the nip, said second endless felt being composed of cellulosic fibres, and said first endless felt being composed of a material having greater wearability than said second endless felt and able to provide cushion within the nip.

2. A dewatering press as described in claim 1 further including a third endless felt positioned about and contacting said second roller; and a fourth endless felt positioned about said third endless felt and about said second press roller, said fourth endless felt overlapping and contacting said third endless felt in the area of the nip, said fourth endless felt being composed of cellulosic fibres, and said third endless felt being composed of a material having greater wearability than said fourth endless felt and able to provide cushion within the nip.

3. A dewatering press as described in claim 1 wherein said second endless felt is composed of cotton.

4. A dewatering press as described in claim 2 wherein said second and fourth endless felts are composed of cotton.

5. A dewatering press as described in claims 1 or 3 wherein said first endless felt is woven and needled using nylon web and is compacted to a high density.

6. A dewatering press as described in claims 2 or 4 wherein said first and third endless felts are woven and needled using nylon web and are compacted to a high density.

7. A method for dewatering a web of liquidcontaining paper comprising the steps of: providing a press assembly including a pair of rollers defining a press nip; passing a first endless felt through said nip, passing a second endless felt through said nip, said second endless felt overlapping said first endless felt while passing through the nip, said second endless felt being composed of cellulosic fibres, said first endless felt being composed of a material having greater wearability than said second endless felt and providing cushion within the nip; and passing a liquid-containing paper web through said nip, said web overlapping said second endless felt such that liquid expressed therefrom will be retained by said second endless felt.

8. A method as described in claim 7 further including the steps of passing a third endless felt and a fourth endless felt through said nip, said fourth endless felt being composed of cellulosic fibres and overlapping said third felt within the nip, said paper web passing between and contacting said second and fourth endless felts as it passes through said nip.

9. A method as described in claim 7 wherein said second felt is composed of cotton.

10. A method as described in claim 8 wherein said second and fourth endless felts are composed of cotton.

11. A method as described in claim 7 or claim 9 wherein said first endless felt is woven and needled using nylon web and is compacted to a high density.

12. A method as described in claim 8 or claim 10 wherein said first arid third endless felts are woven and needled using nylon web and are compacted to a high density.

13. A dewatering press for drying fabrics such as moisture-containing paper webs, the press being substantially as herein described with reference to and as illustrated by the accompanying drawings.

14. A method for dewatering a web of liquidcontaining paper, the method being substantially as herein described with reference to and as illustrated by the accompanying drawings.