US3357880A - Apparatus for making fibrous webs - Google Patents

Description

Dec. 12, 1967 D. R. CURTIS APPARATUS FOR MAKING FIBROUS WEBS Filed March 23, 1965 anmwkak pm jp KfMR/kw JMRAWJ United States Patent M 3,357,880 APPARATUS FOR MAKING FIBROUS WEBS Donald R. Curtis, Appleton, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Mar. 23, 1965, Ser. No. 442,125 4 Claims. (Cl. 162344) ABSTRACT OF THE DISCLOSURE A portion of a paper machine is disclosed where paper stock discharged from a headbox is deposited on a web forming wire inclined upwardly from a breast roll toward a couch roll and having a suction box assembly mounted beneath the top strand of the wire with the suction box adjustably spaced from the breast roll.

This invention relates to a method and apparatus for making formed fibrous webs and is particularly applicable to the production of paper.

Existing machines for the production of paper are principally of two types, the fourdrinier machine and the cylinder machine.

In the fourdrinier machine, an almost negligibly small amount of Water removal takes place by gravity flow through the Woven wire cloth. A large part of the water removal is effected by the suction action of the table rolls, further water is removed at the vacuum fiat boxes and still further dewatering is achieved in the suction zone of the couch roll. Because of this intermittent action involved, a large portion of the wire cloth is inefiective in removing water and this results in a very large machine occupying a great deal of space. Also the frictional drag between the wire cloth and the surface of the vacuum boxes requires high energy input to drive the machine and results in rapid wear of the wire cloth. A further disadvantage is that, particularly at high speeds, considerable disturbance of the structure of the web occurs at each table roll with resulting disturbance of the uniformity of formation and loss of fine material through the openings in the wire cloth. 7

In the cylinder machine, formation of the web is continuous, resulting in a more compact apparatus. However, the forces causing flow of water through the cylinder are low, being limited to the hydrostatic head resulting from the difference in level between the outside and inside of the cylinder. For this reason, the speed attainable is low as is the maximum weight of web which can be formed on any one cylinder. A further reason for relatively low speed is the tendency of centrifugal force to throw the sheet off the cylinder.

In an effort to approach the speed and web density capabilities of a fourdrinier but with compactness heretofore achieved with cylinder machines, a third type of machine has been proposed that has an endless screen traveling upwardly at an angle during its passage through a part or the entire paper-forming zone of a papermaking machine. In a machine of this kind the pulp is floated onto the screen from above, for instance through a flow box, and the water is drained through the screen either freely, or draining is accelerated by providing suction boxes below the aforesaid flow box under the inclined screen. However, this causes the fibers in the suction zone above the suction box to be deposited very rapidly onto the screen which causes a less satisfactory felting of the fibers with one another than is obtained in a cylinder machine.

It is an object of the present invention to provide an improved papermaking machine having an inclined wire screen which will make it possible to obtain the various advantages in paper making heretofore obatinable only 3,357,880 Patented Dec. 12, 1967 with fourdrinier machines but the compactness of cylinder machines.

It is another object of the present invention to make provision in such a machine for greater control of the web formation and water drain than has been achieved by the aforementioned prior art practice of floating pulp onto an inclined screen.

According to a preferred embodiment of the present invention a pressure type headbox is provided to discharge pulp under pressure and through an adjustable slice onto a wire screen moving upwardly along an incline. A suction box assembly is mounted ahead of the slice and beneath the screen. The position of the suction box is adjustable so that it can be moved toward and away from the slice opening along the same slope as the wire screen that moves over the box assembly. The inclined Wire screen, the suction box assembly along with a breast roll, couch roll and tensioning roll, all provide an assembly that can be raised and lowered relative to the slice opening as well as being adjustably tiltable to provide selected angles of incline for the web forming screen. Thus a machine as described is especially adapted for operation With a Wide range of pulp densities and in particular the heavier weight pulps such as are used to make boxboard. Experiments have established that with the described arrangement it is possible to produce paper sheets in the range of 5 to 25 pounds per thousand square feet having moisture consistencies ranging from 2.2% to 11.8% under operating conditions as set forth in the following table.

Angle of Minimum Velocity Minimum Velocity Screen Minimum Speed Head to Start Flow Head to Maintain (deg) of Screen (f.p.m.) Up Incline (inches) Flow up Incline (inches) Furthermore, it was discovered that at each angle the desired web formation can be attained'with screen speed increased to a selected higher speed if the'velocity head is increased by an amount equal (in feet) to the difference between the square of the selected higher screen speed (in feet per second) minus the square of the minimum flow maintaining screen speed (in feet per second) divided 1 is determined that aperforated web supporting surface by twice acceleration due to gravity. Thus according to one practice of the method of forming a web according to the present invention pulp is directed along an upwardly inclined forming angle of 30 degrees. For this angle it must move up the 30 incline 300 feet per minute (i.e., 5 feet per second) and the pulp requires a velocity head of 24 inches to start flow up the incline followed by a velocity head of 5 inches to maintain flow up the incline;

. Then the speed of the supporting surface is increased to 1800 feet per minute (i.e., 30 feet per second) while increasing the velocity head of the pulp by 13.6 feet (i.e., 163 inches) to 168 inches.

Other objects and features of the present invention will appear from the following more detailed descrip- 3 indicated by the reference numeral 10 and is shown pro-'- tion with reference to the accompanying drawing which shows a side view, partly in section, of a web forming apparatus according to the present invention.

Referring to the drawing, a pressurized headbox is vided with an optional battle wall 11 spaced to the rear of a front wall 12 to define a pond delivering chamber 13 open to discharge through a slice 14. The pulp is discharged from headbox 10 through slice 14 and on to a web forming wire screen 15.

Pulp from a suitable supply (not shown) flows through a delivery conduit 16 and as indicated by arrows, through a manifold 17 into headbox 10. Rectifier rolls 18 are provided within headbox for preventing the build-up of minor flow irregularities as the pulp flows through the headbox.

The slice opening 14 is defined by a lower lip 20 and an adjustable upper lip 21 hinged to the lower edge of front wall 12. The usual rods 22 are provided for adjusting the position of the upper lip 21 and the opening of slice 14.

p The web forming wire screen 15 is looped around a breast roll 25, a couch roll 26 and a tension applying roll 27. The breast roll 25 and couch roll 26 are journaled in a pair of laterally spaced arms 28. The tension applying roll 27 is journaled in a pair of pivotal arms 29, each of which is pivotally connected to an arm 28 as shown at 30. Breast roll 25 and couch roll 26 are also journaled in support brackets 32, 33 mounted on-top of support column assemblies 34, 35.

Column assembly 35 also supports a platform 37 with brackets 38 bolted thereon for carrying a guide roll 39 for biasing a downward running portion of wire screen 15in the manner shown.

As shown in the drawing, column 35 is substantially taller than column 34 to support breast roll 25, couch roll 26 and forming wire screen 15 in the desired upwardly inclined position. While the position of breast roll 25 is determined by the position of lower lip 20 of headbox 10, the elevation of couch roll 26 may be changed to change the angle of incline of the top strand of screen 15. Column assembly 35 includes a section 36 which may be replaced by taller or shorter sections which will change the elevation of the couch .roll 26 and the angle of incline of the top strand of wire screen 15. Relatively small changes in the elevation of bracket 33 may be achieved by one or more shims placed, for example, between section 36 and bracket 33. To facilitate such changing of the elevation of bracket 33, the arms 28 are each provided with a lug 40 projecting beyond column535. A jack assembly 41 is arranged beneath lug 40 and includes a lift screw 42 that is rotatable within the assembly 41 to rise and engage the lower surface of the lug 40 and thereby lift the lug end 40 of arm 28 along with bracket 33 and couch roll 26.

A suction box assembly 45 is supported by the arms 28 with the top 46 of assembly 45 beneath the upwardly moving strand of wire screen 15. The arms 28 carry the suction box assembly on a surface 47 of greater length than the bottom of box assembly 45. A pair of surfaces 48, 49 perpendicular with surface 47 cooperate therewith to define a notch 50 in arms 28. The suction box assembly 45 is arranged within the notch 50 on the surface 47 and spaced from the surfaces 48, 49. The position of box assembly 45 on surface 47 is made adjustable by means, such as, for example, a pair of threaded bolts 51, 52 turned in threaded bores 53, 54 in the surfaces 48, 49, respectively. The suction box assembly 45 includes internal walls 55, 56 that divide the box into separate compartments. Conduits 57, 58, 59 from such as a suction pump (not shown) are arranged with one connected to each compartment in box assembly 45. When bolts 51, 52 are turned relative to bores 53, 54 the entire box assembly 45 is moved along surface 47 and areas of the box top 46 through which suction is drawn, via conduits 47, 58, 59, are thereby moved toward or away from headbox 10 and the slice opening 14.

The web of paper formed on wire screen 15 is removed therefrom by a felt 60 that passes over screen 15 and between a plain or suction pickup roll 61 and couch roll 26. Felt 60 may be guided between rolls 61 and.26 by a guide roll 62. Roll 61 may be provided with a perforated shell and a fixed internal suction box 63. As wire screen 15 and felt 60 pass between the turning rolls 61, 26 a suction drawn through suction box 63 lifts the newly formed paper web off of the top side of screen 15 and transfers it to the bottom surface of felt 60. If roll 61 is a plain roll transfer is effected by the web adhering to felt 60.

In the operation of the described apparatus according to the method of the present invention, pulp is pumped (by means not shown) through delivery conduit 16, and manifold 17 into headbox 10. The pressure of delivered pulp is increased until the pressure head of pulp in chamber 13 proides a discharge velocity through slice 14 sufficient to cause pulp to flow up the incline of wire screen 15. The arrangement for controlling the pressure within headbox 10 is not the subject of the present invention and may be of any of the well-known arrangements such as are disclosed, for example, in US. Patents 2,609,822; 2,736,246; 2,901,040; and 3,060,955. As wire screen 15 is brought up to operating speed (by driving means not shown), the pressure head in chamber 13 is adjusted to provide a discharge velocity through slice 14 sufiicient to maintain continued web formation on the upwardly moving wire screen. As thepulp emerges from the slice 14 and is deposited on wire screen 15, the pulp on screen 15 immediately passes over suction box assembly 45 and is exposed to the dewatering action of a suction drawn through conduits 57, 58, 59. The web is then carried by wire screen 15 over couch roll 26 where suction drawn through box 63 within suction pickup roll 61 transfers the web from the top side of wire screen 15 to the bottom side of felt which then carries the web along for further processing which may include apparatus similar to that described which may form additional layers of web for application to the bottom side of the web carried by felt 60, to thus make a multi-ply sheet of fibrous material. When the desired number of plys have been provided, the sheet is then passed to press and drying assemblies in the usual manner.

The apparatus and operation that has been described provides great flexibility for control to achieve desired web density and quality with a compact apparatus operating economically and effectively at high speed. That is, to achieve desired web density various factors may be controlled including the density of the pulp, the pressure head in the headbox 10 and the velocity head discharged through slice 14, the profile of slice 14 -(by rods 22), the angle of incline of wire screen 15 and its speed, the vacuum drawn through box assembly 45 and the position of the suction box assembly relative to the slice 14. Thus it has been shown that the present invention provides a unique apparatus and method of forming a fibrous web from an aqueous pulp, and accomplishes the objects that have been set forth as well as others that will occur to those skilled in such arts.

Modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention and thus the scope of this invention is intended to be limited only by the scope of the claims, such as are, or may hereafter be, appended hereto.

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

1. A paper making machine comprising an inclined web forming assembly having a longitudinally spaced breast roll and couch roll and an endless screen looped over said breast roll and couch roll, support structure supporting said breast roll at a first elevation and said couch roll at an elevation higher than said breast roll with the top strand of said screen at an angle of incline upwardly toward said couch roll, driving means connected to said screen to move the top strand thereof up an inclined path from said'breast roll toward said couch roll, a suction box assembly mounted beneath said top strand and on said support structure, an adjust-able spacing device connecting a portion of said support structure to a portion of said box assembly for positioning said box assembly along said support structure toward and away from said breast roll upon adjusting said spacing device, and a headbox having a slice discharge and walls for containing pulp therein under a head higher than said slice to discharge pulp from said slice under the pressure of said head, said headbox being arranged with said slice over said top strand and transverse thereto to discharge pulp up said incline of said web forming screen.

2. A paper making machine comprising an inclined web forming assembly having a pair of laterally spaced support arms with a longitudinally spaced breast roll and couch roll journaled transversely therein and an endless screen looped over said breast roll and couch roll, support structure supporting said breast roll at a first elevation, and said couch roll at an elevation higher than said breast roll with the top strand of said screen at an angle of incline upwardly toward said couch roll, driving means connected to said screen to move the top strand thereof up an inclined path from said breast roll toward said souch roll, each of said support arms having a flat upper surface parallel to said top strand of said wire, a suction box assembly mounted beneath said top strand and on said upper surfaces, an adjustable spacing device connectnig a portion of said support arm to a portion of said box assembly to slide said box assembly along said upper surface toward and away from said breast roll upon adjusting said spacing device, and headbox having a slice discharge and walls for containing pulp therein under a head higher than said slice to discharge pulp from said slice under the pressure of said head, said headbox being arranged with said slice over said top strand and transverse thereto to discharge pulp up said incline of said web forming screen.

3. A paper making machine comprising an inclined web forming assembly having a pair of laterally spaced sup port arms with a longitudinally spaced breast roll and couch roll journaled transversely therein and an endless screen looped over said breast roll and couch roll, support structure supporting said breast roll at a first elevation and said couch roll at an elevation higher than said breast roll with the top strand of said screen at an angle of incline of about 15 to 30 degrees, driving means connected to said screen to move the top strand thereof up an inclined path from said breast roll toward said couch roll, each of said support arms having a flat upper surface parallel to said top strand of said wire, a suction box assembly mounted beneath said top strand and on said upper surfaces, an adjustable spacing device connecting a portion of said support arm to a portion of said box assembly to slide said box assembly along said upper surface toward and away from said breast roll upon adjusting said spacing device, and a headbox having a slice discharge and walls for containing pulp therein under a head higher than said slice to discharge pulp from said slice under the pressure of said head, said headbox being arranged with said slice over said top strand and transverse thereto to discharge pulp up said incline of said web forming screen.

4. A paper making machine comprising an inclined web forming assembly having a pair of laterally spaced support arms with a longitudinally spaced breast roll and couch roll journaled transversely therein and an endless screen looped over said breast roll and couch roll, a first support column supporting said breast roll at a first elevation, an adjustable height second support column supporting said couch roll at an elevation higher than said breast roll and the top strand of said screen at an angle of incline of about 15 to 30 degrees, driving means connected to said screen to move the top strand thereof up an inclined path from said breast roll toward said couch roll, each of said support arms having a fiat upper surface parallel to said top strand of said wire, a suction box assembly mounted beneath said top strand and on said upper surfaces, a threaded bolt parallel to said upper surfaces threadedly connecting a portion of said support arm to a portion of said box assembly to slide said box assembly along said upper surface toward and away from said breast roll upon turning said bolt, a headbox having an adjustable slice discharge and walls for containing pulp therein under a head higher than said slice to discharge pulp from said slice under the pres sure of said head, said headbox being arranged with said slice over said top strand and transverse thereto to discharge pulp up said incline of said web forming screen.

References Cited UNITED STATES PATENTS 2,890,149 6/1959 Muller 16235O X S. LEON BASHORE, Acting Primary Examiner.

DONALL H. SYLVESTER, Examiner.

A. C. HODGSON, Assistant Examiner.

Claims (1)

1. A PAPER MAKING MACHINE COMPRISING AN INCLINED WEB FORMING ASSEMBLY HAVING A LONGITUDNALLY SPACED BREAST ROLL AND COUCH ROLL AND AN ENDLESS SCREEN LOOPED OVER SAID BREAST ROLL AND COUCH ROLL, SUPPORT STRUCTURE SUPPORTING SAID BREAST ROLL AT A FINE ELEVATION AND SAID COUCH ROLL AT AN ELEVATION HIGHER THAN SAID BREAST ROLL WITH THE TOP STRAND OF SAID SCREEN AT AN ANGEL OF INCLINE UPWARDLY TOWARD SAID COUCH ROLL, DRIVING MEANS CONNECTED TO SAID SCREEN TO MOVE THE TOP STRND THEREOF UP AN INCLINED PATH FROM SAID BREAST ROLL TOWARD SAID COUCH ROLL, A SUCTION BOX ASSEMBLY MOUNTED BENEATH SAID TOP STRAND AND ON SAID SUPPORT STRUCTURE, AN ADJUSTABLE SPACING DEVICE CONNECTING A PORTION OF SAID SUPPORT STRUCTURE TO A PORTION OF SAID BOX ASSEMBLY FOR POSITIONING SAID BOX ASSEMBLY ALONG SAID SUPPORT STRUCTURE TOWARD AND AWAY FROM SAID BREAST ROLL UPON ADJUSTING SAID SPACING DEVICE, AND A HEADBOX HAVING A SLICE DISCHARGE AND WALLS FOR CONTAINING PULP THEREIN UNDER A HEAD HIGHER THAN SAID SLICE TO DISCHARGE PULP FROM SAID SLICE UNDER THE PRESSURE OF SAID HEAD, SAID HEADBOX BEING ARRANGED WITH SAID SLICE OVER SAID TOP STRAND AND TRANSVERSE THERETO TO DISCHARGE PULP UP SAID INCLINE OF SAID WEB FORMING SCREEN.

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