US3177113A

US3177113A - Chromium coated papermaking wire

Info

Publication number: US3177113A
Application number: US304869A
Authority: US
Inventors: Martin A Golden; John I Vlossak
Original assignee: Ultra Plating Corp
Current assignee: Ultra Plating Corp
Priority date: 1963-08-27
Filing date: 1963-08-27
Publication date: 1965-04-06
Anticipated expiration: 1982-04-06
Also published as: AT262044B; ES304481A1; FI44522B; CH426465A; SE309716B; NL6409857A; GB1024717A; DE1461165A1; BE652305A; NO124698B

Description

April 6, 1965 OL ET'AL 3,177,113

CHROMIUM COATED PAPERMAKING WIRE Filed Aug. 27, 1963 INVENTORS MARTIN A, LDEN JOHN I.VL SAK BY Vii/40W ATTORNEY United States Patent G Filed Aug. 27, 1963, Ser. No. 304,869 8 Claims. (Cl. 162-348) The present invention relates to metal wires for use on papermaking machines and it more specifically resides in such a wire coated with chromium to enhance its durability and utility.-

Continuous, foraminous metallic belts, or wires? are used on papermaking machines of various types, including Fourdrinier machines. cylinder machines. inver-form machines, verti-form machines and others. Wires most commonly used today are woven wire fabrics. although foraminous sheets are also being developed. The metals commonly 'used for the strands of such wires are Phosphor bronze, bronze, brass, stainless stecl'and others. The wire is the most important single part of the papermaking machine, since the paper web is formed from a suspension of paper fibers in liquid on and by virtue of the wire. In the Fourdrinier machine this is accomplished by depositing the suspension of paper fibers from a head box onto the rapidly moving wire. which permits the moisture to drain through its interstices leaving a web of paper on the 'wire to be delivered bythe wire to the first press part of the machine. Drainage and formation of the web is accelerated by table rolls and suction boxes, over which the wire slides, so that the driest possible paper web is presented to the press part, which presses more moisture from the web before the web is passed through a drier part of the machine. Papers of good uniform quality can be etiiciently produced only if the wire is itself smooth and uniform, and provides maximum drainage through its interstices.

However. many forces and conditions are constantly at work to deteriorate the wires rapidly. requiring frequent replacement with the attendant high cost of replacement of the wires and shutdown of the machine. The high speed travel of the continuous wire about the rolls of the machine causes rapid flexing of the wire, resulting. if the wire is too stiff. in premature fatigue failures. that is. failures due'to fatigue while the wireis otherwise still usable. Hence. flexibility is an important characteristic of a good Fourdrinier wire. Sliding of the wire'over the suction boxes and table rolls abrades the surface of the wire, making resistance to abrasion an important property of a Fourdrinier wire. processes used. Fourdrinier wires are subjected to more or less corrosive solutions that pit the surface of, and ultimately consume the wire. Hence. resistance to corrosion is a necessary attribute of a Fourdrinier wire. must resist deformation which may result from lumps in the stock and which leave marks and irregularities in the web. The wire must be made of a hard metal. sothat it will retain its shape and smoothness, so as not to snag paper fibers that will clog its interstices and impede drainage. It must also have a high tensile strength to withstand stress even after substantial deterioration.

Research has been and is carried on continuously in an effort to improve the characteristics of Fourdrinier wires and much-progress has been made. New metals and coatings have been developed to improve wires. However, changes in papermaking machines and processes make new demands on the delicate wires so that the life of a wire, in some applications, continues to be as short as a few days. The suggestion that Fourdrinier wires be coated with chromium was pursued, but experience establis hed that the chromium coating made the Fourdrinier wire so brittle as to cause premature fatigue failures. ren- Depending upon the papermaking The wire I 3,177,113 Ice Patented Apr. 6, 1965 dcring the protective capabilities of the chromium coating useless. However, the present invention provides a chromium coated Fourdrinier wire that is not subject to premature fatigue failures. In addition, the present invention provides a Fourdrinier wire of greatly enhanced wear qualities without materially increased stiffness by electroplating a woven Fourdrinier wire so that the surfaces subjected to wear have a thicker and harder coating of chromium, while the other surfaces have a coating of lesser thickness and hardness.

However, a wire made according to the present invention also manifests a number of hitherto wholly unexpected advantages. resulting in a surprisingly superior Fourdrinicr wire. For example, it was discovered that even after the chromium coating was abraded through and the exposed wire strands corroded from under the chromium coating. the coating continued to support the strand and the wire displayed twice the abrasion resistance of an uncoated wire. The tensile strength of the strands was found to be substantially increased. Where fissures in the chromium coating occur, exposing the strand, the strand manifests about twice the resistance to corrosion as would be expected and as was experienced with other coatings, such as nickel. Worn strands of other Fourdrinier wires develop burs projecting outward along the edges of the worn surfaces, and these burs catch fibers, clogging the interstices of the wire and reducing drainage. The chromium coated wires of the present invention, it was discovered, did not form burs, but wore smoothly.

Accordingly, it is an object of the present invention to provide a chromium coated papermaking wire that is not subject to premature fatigue failures.

It is another object of the present invention to provide a papermaking wire having great resistance to abrasion.

It is another object of the present invention to provide a papermaking wire that is highly corrosion resistant.

It is another object of the present invention to provide a papermaking wire having improved hardness.

It is another object of the present invention to provide a papermaking wire that retains a smooth surface throughout its use.

It is another object of the present invention to provide a papermaking wire that resists the formation of a sulfide scale.

It is another object of the present invention to provide a papermaking wire that resists the adherence of pitch on the surface of the strands to require cleaning.

It is another object of the present invention to provide a papermaking wire that resists formation of a scale of paper coatings, such as aluminum resinate, on its surface.

It is another object of the present invention to provide a papermaking wire that is particularly well adapted for use in making such papers as photographic or facsimile papers that are sensitive to cationic or metallic contamination.

It is another object of the present invention to provide a papermaking wire that resists deformation.

The foregoing and other objects will appear in the description to follow. In the description, reference is made to .the accompanying drawing which forms a part hereof and in which there is shown by way of illustration a specific embodiment in which this invention may be practiced. This embodiment will be described in sufiicient detail to enable those skilled in the art to practice this invention, but it is to be understood that other embodiments of the invention may be used and that structural changes may be made in the embodiment described without departing from the scope of the invention. Consequently, the following detailed description is not to be taken in-a limiting sense; instead, the scope of the present invention is best defined by the appended claims.

In the drawings:

FIG. 1 illustrates a papermaking wire embodying the present invention mounted on a Fourdrinier papermaking machine,

FIG. 2 is a portion of the wire shown in FIG. 1 taken in section along the line 22 in FIG. 1,

FIG. 3 is a portion of the wire shown in FIG. 1 taken in section along the line 3-3 in FIG. 1.

Refering now specifically to the drawings, in FIG. 1 a

Fourdrinier wire 1 of the present invention is shown' mounted on a diagrammatic representation of a Fourdrinier papermaking machine so as to illustrate more clearly the use of this product and its advantages. However, it is not to be inferred from this specfic embodiment for use on Fourdrinier machines that the invention is limited specifically to Fourdrinier wires. On the contrary, the present invention relates to all papermaking wires for all types of machines and its embodiment in Fourdrinier wires is but a single, though important, application of the present invention. Beginning at the left side of FIG. 1, the Fourdrinier wire 1 passes over a breast roll 2 as it moves in a clockwise direction; next the Fourdrinier wire 1 passes over a plurality of table rolls 3; then it slides over a plurality of suction boxes 4, and about a couch roll 5; then it moves to the left under a stretch roll 6, over a guide roll 7 and under a return roll 7a, and back to the breast roll 2. Frequently only the couch roll is driven and the table rolls 3, the breast roll 2, the stretch roll 6, guide roll 7 and the return rolls 7a are idlers, although in some applications other rolls may also be driven.

The paper fiber suspension (not shown) is fed on the top, or papermaking side 8, of the Fourdrinier wire 1 just above the breast roll 2 from a container known as a head box (notshown). The wire travels at a high rate of speed carrying the wet pulp over the table rolls 3 which aid in the removal of the water from the pulp through the interstices of the Fourdrinier wire 1. By this time the pulp has developed into a thin, wet web of fibers (not shown), and as it passes over the suction boxes 4 the vacuum in the boxes 4 draws more of the moisture from the web and mats the fibers, so that it is a well defined continuous web (not shown) by the time it .reaches the couch roll 5, which in some applications is a suction roll; From the couch roll 5, the web is usually picked up on a felt (not shown) and drawn through the first press part (not shown) of the papermaking machine. In some applications, a Fourdrinier wire 1 may be subjected to further strains by the use of a deflector blade (not shown) which scrapes against the underside, or suction box side 9 of the wire, and

o v.) sometimes machlnes are provided with shake mechanisms '(not shown) which will oscillate the wire 1 near the breast roll 2 to help disburse the suspended fibers on the wire.

FIG. 2 illustrates a small portion of the wire 1 shown in FIG. 1 taken along the line 2-2, and FIG. 3 illustrates a small portion of the wire 1 in section, taken along the line 3-3 in FIG. 1. In the Fourdrinier machine the upper side of the wire 1 is subject to little, if any, wear and this will be referred to as the papermaking side 8. However the' lower. side of the wire 1 is subjected to a great deal of wear and will be called the suction box side 9. In some types of machines, the wear side of the wire may be the papermaking side, and in other applications there may be a wear side of the wire, but neither a papermaking side nor a suction box side, properly speaking. In FIG. 2 a single weft strand 10 is shown in section extending horizontally across the page and a plurality of warp strands 11 are shown above and beneath the weft strand 10. In FIG. 3, a single warp strand 11 is illustrated in section extending across the page with a plurality of weft strands 10 above and beneath the warp itrand 11. Phosphor-bronze cores 12 of the weft strands [0 are illustrated with coatings of chromium 13 about iheir surfaces, but frequently brass weft strands 10 are also used. Similarly, the warp strands 11 have Phosphorbronze cores 14 with chromium coatings 15 about their surfaces. About the knuckles 16 of the weft strand 10 in FIG. 2 reed dents 17 are formed. These reed dents 17 are entirely covered by the chromium coating 13 as are all other surface deformities which might occur in the

strands

10 or 11.

In the drawing, the thicknesses of the chromium. coatings 13 and 15 relative to the size of the

cores

12 and 14 are greatly exaggerated in order that the structure of the present invention might be more clearly shown. In practice, the

core strands

12 and 14 may be of diameters ranging from 0.016 to 0.003 inch (a twisted cable, as dis tinguished from the solid cores shown here, might have an outer diameter as great as 0.032 inch, but its individual strands would be within the range indicated), and as will be brought out in greater detail later the thickness of the coatings 13 and 15 will be less than 0.001 inch. Hence,

' if these wire strands l0 and 11 were drawn to scale, the

coatings 13 and 15 would have thickness little greater than that of 'a pencil mark.

It is to be noted that the chromium coating 13 about the weft strand 10 is substantially thicker on the suction box side 9 of the wire 1 than on the papermaking side 8, except at the interfaces between the ,weft strand 10 and the warp strand llwhere the chromium coatings 13 and 15 are both extremely thin. Also, the chromium coating 15 about the warp strands 11 is substantially thicker on the suction box side 9 of the wire 1 than on the papermaking side 8, except at the interface between

strands

10 and 11.

Wires embodying the present invention are made in the following manner. First, strands of any of the commonly used alloys or metals are woven together in the usual way, except, of course, in those cases where the wire is made of a foraminous sheet. electroplated with chromium to the dimensions disclosed herein. As a result, the coating at the interfaces of the crossing

strands

10 and 11, where there is no wear, is at a minimum. Hence, flexibility is promoted without loss of abrasion resistance. Also, stress points and other deformities, such as reed dents 17, which have had greater vulnerability to corrosion, are covered.

The mentioned differential in thickness of the coating 13 and 15 between the papermaking side 8 and the suction box side 9 is maintained to ensure maximum strengthening of the wire 1 against wear of various sorts with a minimum loss of necessary flexibility to avoid'premature fatigue failure. In. commercial embodiments, the thickness of the coating 13 and 15 on the suction box and papermaking sides 9 and 8, respectively, are on the order of 0.0001 inch and 0.00005 inch, and although an absolute commercial standard has not been fixed, a tentative standard of 0.000070 inch on the suction box side 9 and 0.000049 inch on the papermaking side 8 is now in practice. Hence, it may be said that the differential in thickness of the chromium coating 13 and 15 between the suction box side 9 and the papermaking side 8, respectively, should be between about one-and-one-half and two to one. Experiments indicate that successful wires could be made having chromium coatings 13 and 15 of thicknesses within a range of 0.000025 to 0.00075 inch on the suction box side 9 and a range of 0.0000125 to 0.0003 on the papermaking side with the above indicated or greater differential in thickness being maintained between the coatings 13 and 15 on the two sides 8 and 9, the thinnest coating being that necessary to continuity of the coating, and the thickest dimension being that allowable on one side of the wire 1 without causing premature fatigue failures. Those extremes, as a practical matter, are of limited application due to the great difference in stress, abrasion, corrosion, etc., to which wires 1 are subjected in different papermaking machines and mills. Hence, commercially acceptable dimensions lie well within the extreme limits established under controlled conditions. as the coating 13 and 15 on the suction box side 9 of the The endless metal belt is then Moreover, just wire 1 may be made thicker by reducing the thickness of the coating 13 and on the papermaktng side 8 of the wire 1 while preserving maximum flexibility, the results are further improved by providing a more ductile coating- 13 and 15 on the papermaking side 8 of the wire 1 where hardness is not necessary, and a harder coating 13 and 15 and the environment within which they are used. These wires may be up to 350 inches wide and .over 400 feet long. The mesh count of the wire may exceed 100. although a mesh count of 75 is common. There are various types of weaves used in papermaking wire, such as a plain, semitwill and full twill, but most commonly a semi-twill weave is used. The normal life of a wire may vary from only a few days to a month and a half, or more. The speed of the movement of the wire on a machine may be as high as 4000 feet per minute.

Great care must be exercised in changing the wires on a Fourdrinier machine so as not to introduce ridges or kinks in the wire, rendering the wire useless or substantially weakening it. During the changes of the Fourdrinier wire, the machine of course must be shut down, and special equipment and a trained crew of men is required to change the wires on the machine. The shutdown time of a machine for a wire change may vary from as little as one hour to over twelve hours, but in any event changing wire on a machine is very expensive in terms of the cost of the wire, the cost of the labor involved and the cost of the lost production as a result of the shutdown time. Hence, the life of the wire is a very important economic factor in the production of paper.

The following table provides test data of actual wires 1 made according to the present invention and experimentally used on different papermaking machines in production of paper. The wire life varies from machine to machine depending upon the corrosiveness of the pulp suspension used, the type of machine used, the speed at which the machine was operated, etc. The length of life shown is measured in 24 hour operating days. hand column is a figure representing the average life of uncoated wires, and in the right hand column is the life of a wire 1 which was coated with chromium according to the present invention.

Average Lite Average Lite ofan t'ncoatcd of (hrtuniitm Wire, days Fnnrtlrinim i \l'irc. days 25 l 33 '15 4'2 (i4 ll? 20 'll 40 (i0 11% 42 mg at) it! 54 10. 7 i 42 On the basis of data thus far collected comparing wires 1 coated according to the present invention with conventional uncoated wires, it may be asserted as a generalization that an undamaged wire Icoated according to the present invention will have a life of at least one and a half times a conventional unconted wire. In addition to the remarkably enhanced life of the wire 1, wires 1 coated according to the present invention, unexpectedly, wore smoothly and did not form radially extending burs, as do the conventional. uncoated wires. These burs formed on the uncoated wires tend to collect pitch and pulp fibers, clogging the interstices of the wire 1 and preventing In the left proper drainage. When this occurs it is necessary to shut down the mcahine and clean the wire with either an acid or a caustic. solution or an organic solvent such as kerosene depending upon the circumstances of the situation. However, since the wires 1 made according to the present invention wear smoothly, the need to clean the wires 1 is obtained.

The remarkable improvement in the life of the wires coated according to the present invention stems from several unexpected results encountered only after actual application of the wire 1. It has been the experience with previous wire coated with different materials, that where a fissure or pin hole developed in the coating exposing the core, a point of high vulnerability to corrosion of the core strand was developed. The opposite result obtained I by the use of chromium coating according to the present invention. Contrary to all expectations the core wire, where exposed either by pin holes, fissures or wear phase in the chromium coating actually exhibited greater resistance to corrosion than an uncoated strand. Also, the tensile strength of the wire 1 embodying the present invention is measurably increased. The ability of the chromium coating to continue to withstand wear even after it wears through at its bottommost surface, and even after a portion of the core is eroded away presented surprising improvement in the life of the wire.

We claim:

1. An endless wire papermaking fabric having a wear side and a side opposite said wear side, the combination comprising: warp strands and weft strands, woven together to present opposing interfaces to each other where said strands cross, and having metallic cores with a chromium coating; said chromium coating on said wear side of said wire having thickness in the range of 0.000025 to 0.00075 inch, and on said opposite side of said wire having thickness in the range of 0.0000125 to 0.0003 inch; and

i said chromium coating being thinnest on said interfaces.

2. In an endless wire for a papermaking machine, the combination comprising: a plurality of weft strands and a plurality of warp strands woven together and presenting interfaces at their intersections; said wire having a wear side and a side opposite said wear side; said strands having metallic cores and a chromium coating between 0.0000125 and 0.00076 inch thick enclosing said cores except at said interfaces; said chromium coating on said wear side being from approximately one-and-one-half times to six times as thick as said chromium coating on said opposite side and being thinnest on said interfaces.

3. A papermaking wire having a wear side and an opposite side to said wear side, and being comprised of a metallic core; and a chromium coating enclosing said core and being of varying thickness in the range of 0.0000125 inch and 0.00075 inch; said chromium coating being approximately one-and-one-half times to twice as thick on said wear side as on said opposite side.

4. A papermaking wire for a Fourdrinier machine composing the combination of Phosphor-bronze warp strands woven together with metallic weft strands, said strands forming interfaces at points of contact; an electrodeposited chromium coating enclosing said strands and varying in thickness within the range of 0.0000125 inch to 0.00075 inch except at said interfaces; said wire having a papermaking side and a suction box side; said chromium coating on said suction box side being approximately oneand-one-half times as thick as said chromium coating on said papermaking side of said Wire.

5. In a papermaking wire the combination comprising: a metallic core structure; a chromium coating enclosing said core in varying thicknesses between 0.0000125 inch and 0.00075 inch; at least one side of said wire being a wear side; said chromium coating on said wear side being harder and thicker than said coating elsewhere on said wire.

6. A wire for papermaking comprising: a plurality of lengthwise copper base metallic wires and a plurality of 7 transverse copper base metallic wires woven with the respective wires crossing overand under one another in a repeated pattern to form a fabric having a papermaking side and a wcarsidc opposite therefrom; the respective wires bearing against one another on their interfaces at the points of crossover and forming knuckles that constitute a wear surface for the wear side and a supporting surface for the 'papermaking side; and a thin chromium film coating said fabric that is thickest on the wear surface and progressively thinnerhtoward the supporting surface.

7. A papermaking wire comprising the combination of a foraminous metal belt having a wear side for receiving a preponderance of abrasive wear in use, and an opposite side for receiving substantially less abrasive wear in normal use of said belt;

and a chromium coating enclosing said foraminous belt, 'having a substantially uniform thickness of about 0.0001 inch on said wear side of said belt, and having a substantially uniform thickness of 0.00005 inch on said opposite side of said belt.

8 1 8. Apapcrmaking wire comprising the combination of a foramainous metal belt having a suction box side and a papermaking side; and a chromium coating ofsubstantially uniform thicknesses on each side of the belt, each thickness being in a range no greater than about 0.0001'inch; said chromium coating on said suction box side of said belt being about one-and-one-half to two times as thick as said coating on said papermaking side of said wire. 1

References Cited by the Examiner UNITED STATES PATENTS DON A. WAITE, Primary Examiner. V

Claims

5. IN A PAPERMAKING WIRE THE COMBINATION COMPRISING: A METALLIC CORE STRUCTURE; A CHROMIUM COATING ENCLOSING SAID CORE IN VARYING THICKNESSES BETWEEN 0.0000125 INXH AND 0.00075 INCH; AT LEAST ONE SIDE OF SAID WIRE BEING A WEAR SIDE; SAID CHROMIUM COATING ON SAID WEAR SIDE BEING A HARDER AND THICKER THAN SAID COATING ELSEWHERE ON SAID WIRE.