CA1153921A - Twin wire web former - Google Patents

Abstract

TWIN WIRE WEB FORMER
ABSTRACT OF THE DISCLOSURE
A twin-wire web forming machine for making paper has a forming roll and a couch roll about which a pair of forming wires are trained in serpentine configuration to provide the formation zone. The forming roll has an imperforate working surface that is circumferentially grooved, to which an open mesh wire sleeve is shrunk to provide a drainage surface whereon the adjourning forming wire is carried. The succeeding couch roll has a single vacuum compartment to assure retention of the formed web on the other forming wire,which passes in contacting relation about the couch roll. The formed web is transferred from the other forming wire for passage to an adjoining press section, transfer being effected using a secondary couch roll having a single vacuum compartment and an opposed lump breaker roll in pressing relation with the web.

Description

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TWIN ~IRE WEB FORMER
This invention is directed to a paper making machine, and in particular to a twin wire web forming section.
In the recent past twin wire web forming has came into its own, and a large number of machines having a wide range of geometries has evolved.
One of the successful earlier twin wire array elements is illustrated in Canadian Patent No.
731,383, issued April 5, 1966, R. de Montigny et al, which employed a pair of forming wires in wrapping arrangement about a suction forming roll and succeeding couch roll having suction and blowing boxes therein.
Many other twin wire machines also utilized a suction forming roll, as exemplified by U.S. Patent 3,236,724, issued February 22, 1966, Wahlstrom, and by U.S. Patent 3j855,057, issued December 17, 1974, ; Hill.
In accordance with the present invention there is provided a twin wire web forming machine : for forming an endless web thereon, including a forming roll and a second roll about which a pair of endless forming wires were trained, having wire guide means spaced from the forming roll to guide .:.
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2 GOK 101-198 the outermost one of the wires in tensioned convergent relation towards the forming roll, the forming roll having the other forming wire in supported relation on the surface of the roll to provide a zone of convergence between the wires for receiving in use a jet of stock therein, wherein the forming roll has a substantially imperforate circumferentially grooved surface, and an open mesh wire sleeve mounted thereon to provide a drainage surface for supporting the other forming wire thereon and dewatering stock therethrough. The second roll includes a suction compartment therein to assure retention of the formed web on the surface of the wire contacting the second roll. A couch roll contained within the same wire loop as the second roll has a lump brea~er roll mounted in cooperating relation therewith. The operative embodiment incorporates the forming wires looped in serpentine relation about the forming roll and the second roll.
It has been found that despite the absence of suction at the forming roll the subject arrangement provides an operative combination whereby effective dewatering and satisfactory formation of the web is achieved. A particular advantage of the present invention is simplification of the forming roll, reduction in cost and in accompanying requirements, with enhanced serviceability and reduced maintenance.
One significant cost saving made possible by the present invention is that, compared with a drilled roll shell which has to be of stainless material, the grooved shell can be of cast iron, having a hard rubber cover applied thereto into which the grooves are cut.
Certain embodiments of the invention are described, reference being made to the accompanying . ' ' ~ ' ' '" '

3 GOK 101-198 drawings, wherein;
FIGURE 1 shows a schematic arrangement in elevation of a machine according to the invention, and FIGURE 2 shows the grooved roll, with the wire sleeve in partially developed relation.
Referring to FIG. 1, the machine 10 has a forming roll 12, a second roll 14 and a couch roll 16. A lump breaker roll 17 is illustrated in cooperation the the couch roll 16.
Fourdrinier wires 18, 20 are carried in tensioned relation on guide rolls as shown. A breast roll 22 guides the wire 18 in convergent relation with wire 20 and the forming roll 12, forming an inlet pocket to receive stock from the slice 24 of headbox 26, the inlet flow header of which is illustrated in phantom about the numeral 26.
The forming roll 12 of FIG. 2 has a grooved hard rubber surface 30 having a Pusey and Jones (P&J) value of 5 wherein the grooves 32 are approximately 0.3" wide by 0.5" deep, having lands 0.1" wide therebetween.
The grooves are usually annular, i.e. separate;
the machining of a single continuous groove, has proved to be difficult.
The overlying mesh 40, illustrated in a developed form as a strip of forming "wire" having a coarse mesh of 10 threads per inch (known as a "10x10"
mesh), a square mesh, usually is applied as a sleeve.
The sleeve is shrunk onto the grooved rubber surface of the roll, using hot water or a steam shower by which to shrink the synthetic material from which the sleeve 40 is formed.
In operation it has been found that the subject machine operates very satisfactorily there being less air pumping than with a drilled roll, while the water removal capability appears quite comparable with that .

of a suction roll of the prior art.
At the same time there is an equipment cost saving by way of a significantly reduced vacuum pump requirement for the machine, and the absence of forming roll suction boxes, together with attendant maintenance costs, while a saving in energv requirement also is achievedJ

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Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A twin wire web forming machine for forming an endless web thereon, including a forming roll and a second roll about which a pair of endless forming wires are trained, having wire guide means spaced from the forming roll to guide the outermost one of the wires in tensioned convergent relation towards the forming roll, the forming roll having the other forming wire in supported relation on the surface of the roll to provide a zone of convergence between said forming wires for receiving stock therebetween, wherein the forming roll has an imperforate circumferentially grooved outer peripheral surface, and an open mesh sleeve mounted thereon to provide a drainage surface, said groove surface being adapted to receive water passing through said open mesh sleeve as said stock is dewatered while passing around said forming roll.

2. The machine as claimed in claim 1, said second roll including a suction compartment therein to assure retention of said web on the surface of said wire contacting the second roll.

3. The machine as claimed in claim 2, including a couch roll contained within the same wire loop as said second roll.

4. The machine as claimed in claim 3 having a lump breaker adjacent said couch roll in spaced relation therewith.

5. The machine as claimed in claim 1, claim 2 or claim 3 wherein said forming wires are looped in serpentine relation about said forming roll and said second roll.

6. A twin wire forming machine as defined in claim 1 wherein said circumferentially grooved surface is formed on said roll by means of circumferential grooves in a resilient sleeve interposed between the body of said roll and said open mesh sleeve.

7. A twin wire forming machine as defined in claim 6 wherein said resilient sleeve is a hard rubber sleeve.

8. A twin wire forming machine as defined in claim 7 wherein said hard rubber has a Pusey and Jones (P & J) hardness value of about five.

9. A twin wire forming machine as defined in claim 1, claim 6 or claim 7, wherein said grooves are about 0.3 inches wide by about 0.5 inches deep and are separated by bands of about 0.1 inches in width.

10. A twin wire forming machine as defined in claim 1, claim 6 or claim 7, wherein said grooves are separate annular grooves.