US3404066A

US3404066A - Suction box cover

Info

Publication number: US3404066A
Application number: US433367A
Authority: US
Inventors: Pierre A Francois
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1965-02-17
Filing date: 1965-02-17
Publication date: 1968-10-01
Anticipated expiration: 1985-10-01

Description

Oct], 1968' I P. A. FRANCOIS 3, I

SUCTION BOX COVER Filed Feb. 17, 1965 a I ,uv G- 4 v wyaf L-l 1 INVENTOR. 2 means FRANCOIS .1. my;

ATTORNEY United States Patent 3,404,066 SUCTION BOX COVER Pierre A. Francois, Indianapolis, Ind., assignor to Union Carbide Corporation, a corporation of New York Filed Feb. 17, 1965', Ser. No. 433,367 3 Claims. (Cl. 162374) ABSTRACT OF THE DISCLOSURE A suction box cover for use in a Fourdrinier paper making machine is provided which comprises a member having an upper surface which faces the Fourdrinier wire and a lower surface which faces the interior of a suction box with a plurality of apertures in the member providing communication between the upper and lower surfaces and a plurality of inserts positioned in a substantial number of the apertures, the inserts having a hard wear resistant coating consisting of, by weight, either (1) about 70 percent tungsten carbide, about 24 percent chromium carbide, and about 6 percent nickel or (2) about 60 percent chromia and about 40 percent chromium.

This invention relates to suction boxes used in Fourdrinier paper making machines and is directed to improvement in the suction box cover associated with such boxes.

Suction boxes are used in conjunction with Fourdrinier paper making machines to facilitate the removal of water from material which, in its finished form, becomes paper. In general, suction boxes are enclosures connected to a source of vacuum which distributes the suction owing to such source to a plurality of holes in its cover. This cover is known as a suction box cover. The suction box cover, with its concomitant holes, is in position such that the vacuum may act on a Fourdrinier wire which is moving in relation to the cover. The Fourdrinier wire carries the material or pulp together with its associated water. The vacuum thus aids in the removal of the water from the pulp material.

The Fourdrinier wire used in modern paper making machines is capable of speeds of the order of 2,000 to 5,000 feet per minute. As the wire contacts the surface of the suction box cover, particularly in the vicinity of its holes, the wire rapidly abra-des or wears, the rate of wear being dependent on the speed of the Fourdrinier wire. In making paper from sulphate or sulphite pulp, for example, the rate of Fourdrinier wire wear is such that replacement is necessary within 14 to 21 days. The condition is aggravated when ground wood pulp is used. Ground wood pulp generally has significant amounts of alumina and silicon carbide interspersed in its fibrous material. The action of these abrasive materials in conjunction with the suction box cover ordinarily reduces the life of the Fourdrinier wire to about 4 to 8 days.

In addition to the wear experienced by the Fourdrinier wire, the suction box cover itself rapidly deteriorates when it is made of end grain of maple or soft plastic. This damage usually manifests itself by the wearing away of the surface of the suction box cover and the creation of channels or grooves in the surface that is left. In this condition the Fourdrinier wire has a strong tendency to freeze in the so-formed channels or grooves resulting in breaking of the wire.

Aside from the rapid wear of the Fourdrinier wire and the suction box covers, the agency of wear, that is friction, acts as a drag on the wire. At the speeds experienced in modern Fourdrinier paper makin this friction increases to a considerable extent the power required for operation. This is true despite the condition of the cover or the wire inasmuch as high friction losses are a ice necessary adjunct to operation with present day suction boxes.

It is well known that Fourdrinier machines are extensively used in the paper making industry despite the fact that shut down time and replacement costs of Fourdrinier wire are very high. The popularity of the Fourdrinier machine and the magnitude of these problems has occasioned considerable effort to improve Fourdrinier wire and suction box cover wear. While suction box covers of many materials have been proposed and tried, few have proven more satisfactory than the end grain of maple. The softer mate-rials, such as rubber and Teflon, wear very rapidly and have a propensity to pick up grit and other abrasive material which accelerate the rate of deterioration of the Fourdrinier wire. Suction box covers made entirely of the more durable hard wear resistant materials such as silicon carbide have proven, in balance, to be more expensive than the traditional end grain of maple. Nonetheless, the art generally recognizes that hard wear resistant materials are the most suitable substitutes for, and materially more satisfactory than, end grain maple if the economics of fabricating covers from such materials can be improved.

The major instrumentality of Fourdrinier wire and suction box cover wear are the edges of the holes in the suction box cover. The vacuum, acting through these holes, urges the wire into the holes causing it to bend, thus contacting the edges under a much greater force than would be the case if the wire was not subjected to the vacuum. The relatively high speeds of the Fourdrinier wire accelerates the wear action of these edges. To fabricate the suction box cover with beveled holes, while reducing wear, has proven more expensive than the cost of shut down time and replacement of the Fourdrinier wire and suction box covers. The reason for this excessive expense is readily apparent from the nature of existing suction box covers in that their holes are integral with the cover itself.

It is the principal object of 'my invention, therefore, to provide an improved suction box which is simple and economic and which avoids the high incidence of Fourdrinie-r wire wear and shut down expense heretofore attributed to the Fourdrinier paper making machine.

It is another object of my invention to provide for a convenient and inexpensive way of improving the wear performance of existing suction box covers.

It is still another object of my invention to provide suction boxes which are capable of allowing a Fourdrinier paper making machine to operate at maximum outputs for periods in excess of those experienced to date.

It is still a further and additional object of my invention to provide for an economical and reliable suction box cover which will reduce the power required to operate a Fourdrinier paper making machine by reducing frictional drag to the Fourdrinier wire from the suction box cover.

These and other objects of my invention will become apparent from the following description, appended claims and drawings in which:

FIGURE 1 is a top plan view of a suction box cover showing a plurality of inserts placed therein;

FIGURE 2 is a sectional view of the suction box cover of FIGURE 1 taken in the plane of line 22 of FIG- URE '1 and slightly enlarged for purposes of illustration, showing a Fourdrinier Wire moving in relation to the cover and the inserts therein and the suction box itself;

FIGURE 3 illustrates an alternate embodiment of my invention depicting a modified insert.

In general, I accomplish the objects of my invention by utilizing a plurality of inserts positioned in at least a substantial number of the apertures present in a suction box cover. These inserts are in position such that at least a portion of an end of each insert contacts a Fourdrinier wire. Each of the inserts is either entirely composed of a hard wear resistant material, or has a hard wear resistant coating in the area thereof which contacts the Fourdrinier wire. Through the inserts are apertures or passages which, with the apertures in the suction box cover, allow for the vacuum present in the suction box to act upon a moving Fourdrinier wire which faces the upper surface of the suction box cover.

Referring more specifically to FIGURE 1, reference numeral 1 designates a typical suction box cover. This cover can be made of any suitable material, such as for example, end grain maple. The suction box cover 1 is provided with a plurality of apertures 2. These apertures serve to position inserts 3 in proper relationship to a Fourdrinier wire and cooperate with such inserts to distribute a vacuum to the aforementioned wire and its load of Water and pulp. Apertures 2 and inserts 3 cooperate as well to define passages to the interior of a suction box for Water extracted by the vacuum. The apertures 2 may be shaped in other than the cylindrical configuration shown as, for example, rectangular slots. Moreover, the apertures 2 can be in any convenient space relation each to the other and relative to the suction box cover 1. Such relationship may be staggered as shown, or, for example, a plurality of rectangular slots with their longest dimension paralleling a diagonal of the suction box cover 1. Moreover, the apertures 2 can be slanted away from the direction of movement of the Fourdrinier wire. With the apertures thus slanted, the vacuum can urge against the wire in the direction of wire travel facilitating water drainage and reducing power requirements.

A typical suction box is shown in FIGURE 2 and indicated therein by reference numeral 11. It normally consists of a six sided structure, including walls 8, 9, 12, suction box cover 1 and two walls (not shown) which enclose a chamber 7. The exact shape of the suction box 11 is, of course, a matter of choice and is indicated here merely for purposes of illustration. Vacuum is supplied to chamber 7 by way of conduit 10 which is in vacuum communication with a source of vacuum (not shown).

The inserts 3, associated with the suction box cover 1, are shown with a hard wear resistant coating 5. Each of the inserts 3 can, however, be entirely composed of the hard wear resistant material. While any hard wear resistant material is within the compass of this invention, it has been found that those materials with a hardness of seven or more on Mohs scale, for example silicon carbide, provide superior wear and friction properties. It is necessary in either of these embodiments of my invention that at least that portion of the inserts which contact a moving Fourdrinier wire 4 be composed of the hard Wear resistant material.

If the inserts 3 are adapted to have the hard wear resistant coating 5, the bond at the interface between coating 5 and insert 3 must be adequate to withstand the forces exerted upon it by virtue of the operation of the suction box 11 in conjunction with Fourdrinier wire 4. The body of the inserts 3 must be of a material, such as stainless steel, to which a hard wear resistant material can be satisfactorily bonded. The coating 5 must, as well, be of a material and applied in such a manner that it will have sufficient strength between the individual constituents thereof to withstand the forces exerted on it from the Fourdrinier wire without failure. These objectives are secured if the coatings 5 on inserts 3 are applied, for example, by a detonation gun or are torch plating process. These processes are completely described in US. Patents 2,714,563 and 3,016,447 respectively. Examples of suitable hard wear resistant materials which can be used as coatings or for the entire insert include a material consisting of about 70 percent 'by weight tungsten carbide, about 24 percent by weight chromium carbide, and about 6 percent by weight nickel; another suitable material consists of about 60 percent by weight chromia and about 40 percent by weight chromium. Other suitable materials include alumina, and composition such as: chromium nickel, tungsten and carbon; chromium and aluminum; and chromium carbide with a composition of 80 percent by weight nickel and 20 percent by weight chromium. The area of the insert 3 or coating 5 which contacts the Fourdrinier wire is processed, as required, to provide its surface with a high polish in order to reduce friction.

It is desirable to have the inserts 3 and their associated hard wear resistant coatings 5 in a position in suction box cover 1 such that the upper surface of the coatings are parallel to the plane of movement of the Fourdrinier wire 4. The direction and hence the plane of wire movement of the Fourdrinier wire is indicated by the arrow of FIG- URE 2. A convenient way of achieving this end is t provide in the suction box cover 1 a space 6 below the desired position of the inserts 3. Before the inserts are placed in apertures 2, a suitable epoxy is placed in space 6. After the inserts 3 are positioned, the epoxy provides sufiicient strength to maintain the desired position during service. Existing suction box covers can be converted to the suction box cover of this invention by fabricating inserts to fit the existing apertures. Alternatively, these apertures can be enlarged to accommodate inserts with any desired dimensional characteristic.

FIGURE 3 is illustrative of a modification of my invention. The insert 20 corresponds to insert 3, shown in FIGURES l and 2, and bears a similar relationship to the suction box cover, suction box, and Fourdrinier wire therein illustrated. However, by virtue of the position of the insert 20 in suction box cover 1 whereby the Fourdrinier wire contacting face 22 is raised above the upper surface 17 of suction box cover 1, the contact between the suction box cover 1 and a moving Fourdrinier wire 4 is minimized or eliminated. This minimization of contact reduces the wear of both the Fourdrinier wire and the suction box cover. The same effect is accomplished by raising inserts 3 above the upper surface of suction box cover 1. In addition, the flange 14 increases the area available for wear resistant material thus assuring longer insert life. The upper face, or Fourdrinier wire contacting face 22, of flange 14 exceeds in its maximum dimension the maximum dimension of the portion of insert 20 which is attached to the flange. As shown in FIGURE 3, the maximum dimension of that portion of the insert which joins lower face 18 of flange 14 is less than the dimension of upper face 22. In assembling a suction cover with inserts such as depicted by insert 20, the apertures 2 of suction box cover 1 and conduit or passage 16 of insert 20 must cooperate to provide vacuum and fluid communication between Fourdrinier wire 4 and chamber 7 of the suction box 11.

The characteristics of the hard wear resistant material of which the insert 20 or the illustrated wear resistant coating 5 of insert 20 can be made should be the same as those applicable to inserts 3 discussed previously. FIG- URE 3 illustrates an important feature applicable to either of the inserts herein illustrated, namely insert 20, or inserts 3. This feature is the beveled or rounded edges shown by reference numeral 21. Heretofore it was not economically possible to round the corners of the suction box cover which contact the moving Fourdrinier wire because these corners were integral with the cover itself. However, with

inserts

3 or 20 it is economically feasible to bevel the corners 21 because each insert is processed individually,

Inasmuch as any material will eventually wear away, it is preferable when the

inserts

3 or 20 have a hard wear resistant coating 5, to make the thickness of such coating normal to the plane of wear of sufficient dimension to insure adequate insert life. A finished coating thickness on the order of 0.008 inch is satisfactory to give an insert life of from three to eight years with normal Fourdrinier wire speeds. Ordinarily, if the coating must be finished to provide a smooth surface, a pre-finishing thickness of 0.015 inch is adequate.

While I have described the present preferred embodiments of my invention, it is to be understood that it may be otherwise embodied without departing from the scope and spirit of the invention.

What is claimed is:

1. A suction box cover for a suction box of the type used with Fourdrinier paper making machines wherein a Fourdrinier wire moves relative to the suction box cover, the suction box cover comprising:

(a) a member having upper and lower surfaces with the upper surface facing the Fourdrinier wire and the lower surface facing the interior of the suction box, the member having a plurality of apertures providing communication between the upper and lower surfaces;

(b) and a plurality of inserts at least partially positioned in a substantial number of the apertures and relative to the upper surface such that at least a portion of an end of each of the inserts contacts the Fourdrinier wire, each of the inserts having a passage cooperating with the apertures to provide communication between the lower surface and the end of the insert that contacts the Fourdrinier wire, and each of the inserts, at least at the end thereof that contacts the Fourdrinier wire, coated with a hard wear resistant coating material selected from the group consisting of by weight (1) a coating consisting of about 70 percent tungsten carbide, about 24 percent chromium carbide and about 6 percent nickel and (2) a coating consisting of about 60 percent chromia and about 40 percent chromium.

2. A suction box cover as claimed in claim 1 wherein the end of each of the inserts that contacts the Fourdrinier wire has beveled edges at least at the points thereof that contact the Fourdrinier wire.

3. A suction box of the type used with Fourdrinier paper making machines wherein a Fourdrinier wire moves relative to the cover of the suction box, the suction box comprising:

(a) an enclosure defining a chamber therein;

(b) means for providing communication between the chamber and a vacuum source;

(0) a suction box cover forming one side of the enclosure, the suction box cover having upper and lower surfaces with the upper surface facing the Fourdrinier wire and the lower surface facing the chamber, the suction box cover having a plurality of apertures providing communication between the upper surface and the chamber;

((1) and a plurality of inserts at least partially positioned in a substantial number of the apertures of the suction box cover, the inserts positioned relative to the upper surface of the suction box cover such that at least a portion of an end of each of the inserts contacts the Fourdrinier wire, each of the inserts having a passage cooperating with the apertures to provide communication between the chamber and the end of the insert that contacts the Fourdrinier wire, and each of the inserts, at least at the end thereof that contacts the Fourdrinier wire, coated with a hard wear resistant coating material selected from the group consisting of, by weight, (1) a coating consisting of about 70 percent tungsten carbide, about 24 percent chromium carbide and about 6 percent nickel and (2) a coating consisting of about 60 percent chromia and about percent chromium.

References Cited UNITED STATES PATENTS 3,067,816 12/1962 Gould 162-374 FOREIGN PATENTS 495,535 11/ 1938 Great Britain.

DONALL H. 'SYLVESTER, Primary Examiner.

40 A. HODGSON, Assistant Examiner.