US3067816A

US3067816A - Apparatus and process for the manufacture of paper

Info

Publication number: US3067816A
Application number: US3688A
Authority: US
Inventors: William E Gould
Original assignee: Carborundum Co
Current assignee: Unifrax 1 LLC
Priority date: 1960-01-20
Filing date: 1960-01-20
Publication date: 1962-12-11
Anticipated expiration: 1979-12-11
Also published as: FI40773B

Description

Dec. 11, 1962 w- E GOULD 3,067,816

APPARATUS AND PROCESS FOR THE MANUFACTURE OF PAPER Filed Jan. 20, 1960 INVENTOR. Will/am E. Gould H/S ATTORNEY United States Patent G 3,067,816 APPARATUS AND PROCESS FOR THE MANUFACTURE OF PAPER William E. Gould, Lewiston, N.Y., assignor to The Carborundum Company, Niagara Fails, N.Y., a corporation of Delaware Filed Jan. 20, 1960, Ser. No. 3,688 8 Claims. (Cl. 162-374) This invention relates to an apparatus `and process for the manufacture of paper. More particularly, it relates to an improved suction box having a cover in which at least the outer surface thereof is composed of a dense, hard ceramic material and a process of making paper therewith.

ln order to produce paper, economically, high-speed machines operating at peak eiciency must be used. The principal'tonnage of paper produced is processed on Fourdrinier machines. At the beginning of the century, the maximum speed at which these machines operated was in the neighborhood of 500 feet per minute. Today, speeds as high as 2,000 feet per minute are common. These increased speeds have substantially decreased the cost of producing paper. Yet, full advantage of this potential has not been possible since the useful life of parts of the machines is materially limited by use at such high speeds.

In a Fourdrinier machine, a slurry of wood pulp and water is fed onto a rapidly moving, endless wire screen. The slurry deposited on the screen generally contains less than 1% wood pulp. The screen provides support for the libers While the iibers are matted'and the water drained olf. A sidewise shaking motion is imparted to the moving screen to help orient the fibers and give better felting action. A large portion ofthe Water will normally drain through the` screen. To increase the speed and efficiency of the drainage, the wire passes over a series of suction boxes. These are generally made of metal and have perforated covers whicharein Contact =with the wire screen. A vacuum, which i's maintained'in the suction boxes draws water from the partially felted sheet into the boxes through the perforations in the cover. The water which is withdrawn may be recirculated unless too strong- 1y colored.

Suction box covers used today are generally made of end grain maple wood. vAlthough the useful life of the covers themselves is adequate, they materially limit the useful life of the wire screen. The slurry passing over the suction box covers on the wire screen invariably has particles of grit and dirt therein. Some of these particles become embedded in Ithe soft wood cover which results in an abrasive action on the rapidly moving wire screen. The covers wear unevenly which also causes undue wear on the wire screen.

At present, the' industry obtainsV in the order of three to tive days life from wire-screens used on the large, high-speed machines. Such screens cost between $3,000 and $5,000 each. In addition to this cost, an extra shift of men is frequently required to change the screen and, of course, use of the machine must be discontinued. The substantial savings involved in anyincrease of the useful life of a wire screen is readily apparent. Even if the useful life of a wire screen could be increased to six days, the savings would be very substantial. Not only would the number of screens used be reduced, but also the screen changes could be made on the weekend, thereby eliminating shutdowns during the working week.

Several alternatives to the normal end grain maple box covers have been tested. Various plastics, rubbers and leather have proved unsuccessful or not fully satisfactory. In general, covers made of these materials have been too soft, wearing the wire rapidly due to the high friction 3,067,816 Patented Dec. 11, 1952 "ice generated between covers of these materials and the wire screen. They pick up grit and other foreign matter which abrades the wire screen. Dimensional stability has also been a problem. For example, nylon has a low coefficient of friction suitable for use as a suction box cover, but it grows or expands due evidently to water absorption.

My invention provides a suction box having a cover which will permit appreciably longer usage of the wire screens. I have found that suction box covers made of hard, dense, ceramic materials will not retain grit and other foreign particles which cause abrading action on the Wire screen. Such covers are dimensionally stable and the coefiicient of friction between the cover and the wire screen is low. Furthermore, the useful life of a cover made according to lmy invention is much longer than the life of the wooden suction box covers now used.

In the drawings, FIGURE 1 is a perspective View illus- Y trating the general arrangement of a paper-making machine in which my suction box cover may be used;

FIGURE 2 is a plan view of a suction box having a cover made according to my invention attached thereto;

FIGURE 3 is a section taken on line III-III of FIG- i URE 2; and

FIGURE 4 is a sectional view of an alternative form of cover made according to my invention.

Referring to FIGURE l, a slurry 10 of wood pulp and Water is fed from a flow box 11 onto a rapidly moving, endless wire screen 12. The screen passes around end rolls 13, at least one of which is driven. The slurry, supported by the wire screen, passes o-ver table rolls 14 and suction boxes 15. Normal drainage and a vacuum maintained in the suction boxes draws orf a large portion of the water. The matted tibers are then passed to drying rolls and sheet rolling equipment, designated generally at 16.

Suction boxes are composed of a wire-contacting cover 20 and a base member 21. Each suction box is connectedto a vacuum source by means such as suction lines 22. The covers 20 are provided with a plurality of openings or perforations 23 whereby the Vacuum maintained in the box draws -water from the partially felted fibers. Generally, each cover is made of a plurality of segments 24, as shown in FIGURE 2.

Atleast the wire-contacting surfaces of suction box covers made according to my invention are composed of a hard, dense ceramic material. I prefer to use an impermeable ceramic having a density of approximately 8O percent or more of its theoretical density and a hardness of seven or more on Mohs scale.

Such materials `may be a self-bonded ceramic, such as high-densit self-bonded silicon carbide. It may be a ceramic-bonded ceramic, such as silicon nitride-bonded silicon carbide. Also suitable are the hard, dense, metalbonded ceramics, such as chromium-bonded alumina, and hard, dense impregnated ceramics, such as zirconiumV diboride impregnated with molybdenum disilicide. Other specific hard,v dense ceramics which can be used include titanium carbide, boron carbide, tungsten carbide, zirconium carbide, titanium boride, zirconium boride, titanium nitride, zirconia, alumina, nitride-bonded silicon carbide, metal-bonded titanium carbide, and metal-bonded tungsten carbide.

The manufacture of hard, dense ceramics is known to the art. For example, Schildhauer et al. U.S. Patent No. 2,907,972 discloses the manufacture of dense silicon car. bide. The preparation of chromium-bonded alumina is disclosed in Conant et al. U.S. Patent No. 2,698,990. The suction box cover may be formed with the openings or perforations 23 therein by standard ceramic forming techniques. The dynamic bearing surfaces should be smooth and are, therefore diamond ground, if necessary.

As shown in FIGURE 3, suction box covers may be made entirely of the hard, dense ceramic material or,

as shown in FIGURE 4, a wire-contacting ceramic section may be bonded to a base plate 31. Also, a layer of hard, dense ceramic could be coated or sprayed on a base plate. Any common material such as steel may be used for the base plate. Preferably, it should be capable of receiving screws or other fastening means directly from the base of the box. Epoxy resins will form a good bond between the ceramic section and the base plate. If a solid ceramic cover is used, clamping means, such as shown in FIGURE 3, are preferable to direct connection between the box base 21 and the cover 20. I have shown a fixed clamp 3S fastened to one side of the box base and a movable clamp 36 mounted on the opposed side of the box base.

While the initial cost of suction boxes made according to my invention is greater than that of suction boxes with maple covers presently used, it is readily apparent that the cost of operating a machine having my suction boxes will he substantially less than one using boxes having the common wood covers. In a test on an operating Fourdrinier iachine, one segment in each of eight suction box covers was made of hard, dense, self-bonded silicon carbide. The remaining segments were end grain maple. The sections of the wire screens which contacted only the ceramic segments showed approximately 30 to 40 percent less wear than the sections of the same wire screens which contacted the end grain maple segments. Furthermore, after three-months operation, the ceramic segments showed practically no wear, whereas the maple segments showed extensive wear. Thus, it is apparent that by use of my invention, the useful lives of 4wire screens and suction box covers are substantially increased. Maintenance costs are materially reduced and the power required to operate the machine is likewise reduced.

While I have described the present preferred embodiments of my invention, it is to be understood that it may be otherwise embodied within the scope of the following claims.

I claim:

l. A suction box cover for a paper-making machine including a moving Wire screen, said cover comprising a screen contacting surface portion that is dense, hard, and wear-resistant and that will not retain grit and other foreign particles which cause abrading action on said screen, said surface portion being composed of an impermeable ceramic material having a hardness of at least 7 on Mohs scale.

2. In paper-making machines in which a moving wirescreen member passes over and contacts a suction box, an improved suction box comprising: a base member and a cover, said cover contacting the moving wire screen and having a dense, hard, wear-resistant, wire contacting surface that will not retain grit and other foreign particles which cause abrading action on said screen, said cover being composed of an impermeable ceramic material having a hardness of at least 7 on Mohs scale.

3. In paper-making machines in which a moving wirescreen member passes over and contacts a suction box, an improved suction box comprising: a base member and a cover, said cover comprising a base plate and a wirecontacting section bonded to said base plate, said section having a wire-contacting surface that is dense, hard, and wear-resistant and that will not retain grit and other foreign particles which cause abrading action on said screen and said wire-contacting section being composed of an impermeable ceramic material having a hardness of at least 7 on Mohs scale.

4. In paper-makingrmachinesin which a moving wirescreen member passes over and contacts a suction box, an improved suction box comprising: a base member and a cover, said cover comprising a plurality of perforated, wire-contacting segments each having a dense, hard, wear-resistant surface that will not retain grit and other foreign particles which cause abrading action on said screen and said wire-contacting segments consisting essentially of an impermeable ceramic material having a hardness of at least 7 on Mohs scale.

5. A suction box cover for a paper-making machine including a moving wire screen, said cover comprising a screen contacting surface portion that is dense, hard, and wear-resistant and that will not retain grit and other foreign particles which cause abrading action on said screen, said surface portion being composed of an impermeable ceramicY material of the character of self-bonded silicon carbide, and having a density of at least percent of its theoretical density and a hardness of at least 7 on Mohs scale.

6. In paper-making machines in which a moving wirescreen member passes over and contacts a suction box, an improved suction box comprising: a base member and a cover, said cover contacting the moving wire screen and having a dense, hard, wear-resistant, wire contacting surface that will not retain grit and other foreign particles which cause abrading action on said screen, said cover being composed of self-bonded silicon carbide, and having a density of at least 80 percent of its theoretical density and a hardness of at least 7 on Mohs scale.

7. In paper-making machines in which a moving wirescreen member passes over and contacts a suction box, an improved suction box comprising: a base member and a cover, said cover comprising a base plate and a wirecontacting section bonded to said base plate, said section having a wire-contacting surface that is dense, hard, and wear-resistant and that will not retain grit and other foreign particles which cause abrading action on said screen and said Wire-contacting section being composed of self-bonded silicon carbide, and having a density of at least 80 percent of its theoretical density and a hardness of at least 7 on Mohs scale.

8. In paper-making machines in which a moving wirescreen member passes over and contacts a suction box, an improved suction box comprising: a base member and a cover, said cover comprising a plurality of perforated, wire-contacting segments each having a dense, hard, wearresistant surface that will not retain grit and other foreign particles which cause abrading action on said screen and said ywire-contacting segments consisting essentially of selfbonded silicon carbide, and having a density of at least 80 percent of its theoretical density and a hardness of at least 7 on Mohs scale.

References Cited in the le of this patent UNITED STATES PATENTS 128,469 Curtis Iuly 2, 1872 1,644,867 Berry Oct. 11, 1927 1,703,010 Manson Feb. 19, 1929 2,215,572 Wilson Sept. 24, 1940 2,602,714 Wheildon July 8, 1952 2,637,091 Nicholson May 5, 1953 FOREIGN PATENTS 770,832 Great Britain June 15, 1955