US2154201A - Manufacture of surfaced felted sheets - Google Patents

Description

April 11, 1939. o. w. FROST MANUFACTURE OF SURFACED FELTED SHEETS 3 Sheets-Sheet l Filed March 23, 1936 April 11, 1939. l o, w. FROST MANUFACTURE OF SURFACED FEL'IED SHEETS Fild March 23, 1936 s Sheets-Sheet 2 wzarra April 11, 1939. o. w. FROST MANUFACTURE OF SURFACED FELTED SHEETS 3 Sheets-Shet 3 Filed March-23, 1956 five/2Z0?" Urcuzff M42055 I my.

"J D. W n n 1 N wk m KW a ANOW R Q w lvillrllnn Patented Apr. 11,1939

PATENT OFFICE 2,154,201 mnmc'roas orsuamonn muran SHE ETS

Orcutt W. Frost, Cloqnet, Minn assignor to Wood v Conversion Company, Cloquet, Mirna, a corporation of Delaware Application March 23,

2 Claims.

The present invention relates to the manufacture of fiber sheets and artificial fiber board with a high strength and uniformity of body structure and with .a characteristic uneven surface. The said surface is one which is generally level, as in a board having an average uniform thickness, but which is locally high or low with respect to the general level, as in a board with local differences in thickness. Another feature of the desired surface is that the highest spots or areas may be levelled or flattened to substantially the same plane, corresponding to miniature plateaus of the same height in a miniature area of hills and valleys. It is another feature. that the said plateau-areas are harder and more dense, and the lower areas are more porous and less dense. Still another feature of the invention is that the body of the board has a-uniformly well felted texture, and that the miniature hills therein at the surfacei are well felted into the body of the board and substantially integral therewith.

The surfaces, above referred to have desirable qualities for decorative appearance when used in a wall-board, either finished or unfinished. The sheet with flattened high spots has a more practical advantage when the sheet is exposed for use in sound deadening. The lower areas being less dense have greater porosity and higher efliciency as sound absorbing area's, than the plateau-areas of the higher spots. A further advantage is that the surface is apparently uneven, yet the high spots may be at one level to provide the plateau plane which determines the caliper of the sheet.

The problem of making a sheet with the required surface is not a difiicult one. Likewise the problem of making a sheet of uniformly well felted texture is not a difiicult one. But to accomplish both tasks together is difficult, because the ready solution of one problem is antagonistic to the other. For example, in the paper-making industry thin and thick sheets of feltmay be formed on a wire by flowing on to the wire a thin slurry of pulp. That consistency which produces an even formation results also in an even top surface. To make an uneven surface, a lumpy, thick or non-homogeneous slurry of pulp may be used, and this does not produce a uniformly well felted body. The present invention is therefore directed to the making of a sheet from a thin slurryto produce uniformity and homogeneity in the texture of the body, and then at an appropriate place disturbing the surface only, to provide the desired characteristics. The process may be carried out intermittently or continuously as will be hereinafter more particularly described,

1936, Serial No. 10,333

The present invention more particularly contemplates the use of a continuous process for producing a board with regular and uniform texture or formation throughout the major portion of its body, and the introduction into the process of a disturbing element for interfering with certain phases of the process which tend to effect a uniform surface, so that the disturbance produces desired breaks in the uniformity of the resulting surface. e

A variety of means may be employed for creating the desired disturbance. The means will of course vary according to the kind of process used and the surface desired, for example whether it be a regular pattern or a nap-hazard or irregular l5 pattern, or whether itbe a deep or shallow variation. The means also may vary for adaptation to the place or step in the process where it becomes effective on the stock. 'In order better to explain the nature of the invention, the general process will be described.

The sheet-making process may be considered to follow generally the process of making paper either as hand-made sheets, or on a cylinder or on a Fourdrinier wire. A uniform water slurry of pulp having about 1% of fibers is placed in co'ntactwith a screen so as to form a fiber felt thereon. As the pulp is dewatered through the screen a sheet is formed with a uniformly felted texture and a uniform surface. In a cylinder machine the screen is a roll or is on a roll, which dips into the slurry. Suction or pressure flow causes motion of water through the screen which holds back the fibers in a felt-formation. As the screen moves out of the slurry water is drained from the mat and later at a suitable consistency the mat may be lifted from the screen. I

In the Fourdrinier process the slurry flows in a constant stream from a head-box onto a moving screen. As the stock is carried away fromthe head-box, water drains from the stock forming the felt, and drainage may be hastened by. suction means. Then pressure may be applied as through press rolls to squeeze out water which does not readily drain, andto compact the felt .to .a desired density. The compression may take place one or more times and either before or after the felt leaves the screen.

In either case the stock changes in moisture content from about 99% to about 50% to 65%, at which time the felt has considerable rigidity and is suitable to be dried into a sheet or board. As the original stock loses water it becomes less plastic under mechanical force. Originally it is substantially .a liquid, flows, and seeks a level. It

is this quality which produces uniform felting in the body, and tends to produce a uniformthickness and a uniform surface. As it loses water it loses its tendency to flow laterally, and becomes subject to vertical compression (assuming it is on a horizontal screen) whereby water is squeezed from it without materially altering the formation.

At earlier stages vertical compression produces lateral flow. At less water content there is a stage where vertical compression does not produce lateral flow. In this stage any vertical compression is a mere anticipation in point of time of pressure from the subsequent general action of the pressing means. Localized pressures at such stage are therefore ineffective to alter the surface.

However, during the stage where vertical pressure will produce lateral flow, localized pressure is effective to alter the-surface so that it is not uniform. It is satisfactory so far as the surface is concerned but it is'unsatisfactory so far as the formation in the body is concerned. The local pressure is effective throughout the whole thickness, and hence the entire body of the board is thinned. Also the lateral movement disturbs the uniformity of formation in the body.

The present invention is based upon disturbing the upper layer or zone of the felted stock at such a stage that the disturbance is more generally confined to the upper layer and generally minimized in the lower layer, whereby the lower layer maintains its natural uniformity of felting, It is furthermore based upon disturbance of the upper layer which is so limited that it does not destroy an effective felted relation between the lower layer and the upper layer. Otherwise, in the dried board there may be loosely held aggregates of fibers which can be picked out or pulled out, as in cutting the board with a tool.

According to this invention only the upper layer is disturbed while the stock at said layer is at a consistency to maintain some permanent indications of the disturbance, and these indications constitute the desired surface. Regularity or irregularity may be obtained, but irregularity is preferred and is the more difficult to obtain. The said indications may be small or large giving respectively diilerent degrees of fineness or coarseness of surface appearance.

One method is to subject the top surface of the stock at a proper consistency to displacing means such for example as to means providing one or more drag surfaces, which means may be fixed or movable or yieldable in various combinations. Another way is to displace the stock by fingers, pins or blades suitably controlled to destroy the uniformity of felting and thickness in the top layer, without destroying its felted union with the bottom layer and without making pronounced separations of stock in the top layer. that the stock may be stationary or be moving continuously and that the disturbing means has a suitable motion relative to the stock. This motion may be compounded so as to give motion in various directions either with or against the stock, or additional motion vertically or horizontally with respect to the plane of the felt.

Figs. 1 to 4 inclusive represent more or less diagrammatically successive steps in the process of producing a fibrous felt from a liquid slurry In any method it is to be appreciated Fig. 5 represents diagrammatically the prior art steps of processing a moist self-sustaining fibrous sheet including trimming, pressing and drying, and stacking the sheets.

Fig. 6 represents conventionally a characteristic surface of a fiber board made in accordance with the present invention.

Fig. 7 represents a longitudinal cross-section of a Fourdrinier machine for continuously forming a wet sheet from a liquid slurry of pulp, showing particularly mechanical means for creating a characteristic surface.

Fig. 8 shows a cross-section of the mechanical surfacing device on the line 8-8 of Fig. 7.

Fig. 9 is a horizontal section on the line 9@ showing the method of mounting the surfacing blade, said section being taken on line 9-9 of Figs. 7 and a.

Fig. 10 is a modified form of surfacing device mounted on a machine similar to that in Fig. 7.

Fig. 11 is a front elevation of said device taken on the line il-ll of Fig. 10.

Fig. 12 is another modified form of surfacing device showing a flexible drag in vertical cross section on the line lZ-IZ of Fig. 13.

Fig. 13 is a front elevation of the device in Fig. 12, partly in section showing weighting means for the drag.

The process is first generally and diagrammatically described with but brief reference to apparatus.

The numeral l0 illustrates a screen onto which is flowed a thin homogeneous slurry ll of pulp of about 1% consistency. Water I2 drains through the screen forming a still highly watered pulp stock l3 on the screen. Water l2 continues to run away, thickening the stock Iii until it reaches a stage indicated at id in Fig. 2. At this stage the top layer is disturbed by means l5 which may be a finger, blade or other device designed and used to produce displacements i6 of stock above an imaginary line I7, and to avoid disturbance below line H. The stock is sufficiently self-sustaining to retain some record of the disturbance. Next, the stock is further dewatered, and to hasten this process suction-may be applied as shown at IS in Fig. 3. This more permanently sets the disturbed portions l9 and makes a more rigid felt 20.

The sheet may now be dried or pressed and dried, or simultaneously dried and pressed. The density of the final sheet is controlled by this question of pressing. Insulating boards of about 17 lbs. per cubic foot require an additional pressing which is exemplified in Fig. 4 by press platens 2l and 22. The screen ID with its stock (from Fig. 3) are placed on bottom platen 2| which has a grid 23 for receiving expressed water. Over the stock 20 a thick cloth sheet or fdrier felt 23 may be placed over the stock as a surface-preserving filter, where there isa suction chamber 24 with grid 25 for removing water expressed from the stock. Such a press may lower the water content considerably, as for example to 65% to 50%. The sheet is then quite rigid and self-sustaining as shown at 26 in Fig. 5.

. Fig.5 is a very diagrammatic representation of subsequent steps well known in the art. The sheet 26 may require trimming or cutting, for which cutting means 28 is supplied. The cut sheets are distributed as at 29 to selected levels in a drier 30 which may vary in style. A plate drier is preferred for drying the sheet between heated platens, indicated at 3|. These are plates which press on both sides of the sheet to boil the water out of it. Pick-up devices 32 urge the sheet forward as it is periodically released from the platens. The sheet in the drier is designated 33. The plates compact the high spots on the sheet to the same general level and provide denser surfaces to the board at such high areas, leaving the lower areas less dense and unflattened. The resulting boards are shown leaving the drier at 34 and are stacked at 35. The flattened high spots give a regular caliper to the sheet, and provide slide-surfaces for one board on another, thereby eliminating danger of tearing or injuring high spots, as would occur in rough treatment of the same boards unfiattened in this way.

Fig. 6 illustrates a characteristic surface and body made by this process. The body 39 of the board is uniform over its various areas and presents a sort of cleavage parallel to the faces 40 and 4|. The cleavage is not in distinct planes, like the cleavage planes in minerals, for example mica, because there are fibrous connections between the apparent irregular laminations. This is a standard condition in felted sheets due to the compression processes whereby the fibers bee come more horizontal as the thickness of the felt is decreased. Such structure makes a stronger board. The face 40 has the flattened high spots 42 and-the irregular low spots 43. High spots 42 are denser, and lie in one plane. They may show diiferences in color and texture because of the different conditions of formation, some being more dense than others. .They may all be different in appearance from the low areas 43,

which have not been subjected directly to pressure from heated platens 3!. Looking upon the surface as'a miniature terrain, the low spots are valleys, and the high spots are mountains, leveled to form plateaus, all of the same altitude.

Another feature of the board is the different density characteristics on the two sides. The top is mottled as to density, leaving softer areas for better sound deadening effect. The bottom is more uniformly dense, and the smaller the valleys and the thicker the board, the greater the uniformity. Greater pressure is exerted on the board over the high spots, and the pressure is transmitted laterally because of the nature of the fiber and the solidity of the felt. Hence the bottom is practically uniform in density where the thickness is one-half inch. The formation is uniform, resulting in uniformity of strength.

Continuous process The invention may be carried out practically in numerous ways, and it is preferred to operate in a continuous process on the Fourdrinier principle. First, the fibers are prepared into a thin uniform slurry. Slightly cooked fibers are preferred, since these are sufliciently soft and pliable to felt readily and to give a desired surface quality. However, the kind and quality. of fiber is subject to change according to the nature of product desired.

The slurry 5U enters any suitable head-box 5|;

. wire and between rolls of group 51, falling into catch basins 69. If desired, water may be more .screen, the less visible its markings.

.deckel straps 11 and I8.

quickly removed by use of a suction device 6|.

Group 58 serves also as the lower part of a series of press rolls complementary to the upper set 62. The rolls on the upper set are arranged to present a tapering zone between them and rolls of group 58, for squeezing the felt gradually. However, before the felt is squeezed it comes into contact with a sheet 63, moving endlessly over idlers 64, and between end rolls 65 and 66. This sheet 63 may be a felt or a screen. A screen may be chosen so as to make some characteristic marking on the top surface. The finer the Beyond the tapered pressing groups 62 and 58, there is a zone where the sheet can expand a little, as between rolls 59 and 61. Then the sheet gets a heavy squeeze between press rolls 68 and 69. The sheet then passes along to the couch roll zone where it leaves both upper and lower wires as shown at Ill. This corresponds to sheet 26 in Fig. 5.

During the travel of the pulp stock from the head-box 5| it becomes dewatered. At'some point it is suitable for treatment to alter .the

surface as above described generally. The point cannot be definitely designated, and it may vary according to speed of wire, consistency of stock, temperature, and various factors. It has been found to vary for unknown factors, and hence provisions are made to locate apparatus to follow the point as it may change. The means generally designated [5 in Fig. 2 is therefore positioned adjustably along the length of the machine. In Figs. 7 and 8 parallel tracks or rails 15 and 16 are provided above the-felt level for mounting the disturbing means. It will be noted that the stock at the head end is liquid, and hence kept on the wire by a common device such as Between the deckel straps there is suspended from the tracks a mechanical device for altering the surface of the felt. Suitable means are provided for adjusting the device. One form comprises bolts 19 set in the rails with longitudinal slots 80 in a suspended bracket plate Bl which carries the device.

One form of device is shown in Figs. '7, 8 and 9.

Generally, this comprises a plurality of teeth or fingers which move to disturb the top layer of the felt F., The teeth may be irregularly disposed and/or moved. The relative motion between the teeth and the felt may vary, and since the felt moves the teeth may be stationary in that direction or partake of a different motion in that direction. Since the felt .does not move crosswise or vertically, the teeth may have crosswise or vertical movement. A satisfactory arrangement has a blade 82, with a right angle flange 83. The blade is cut into irregular teeth (Fig. 8) 84. r

Flange 83 is carried by the heads of pivot pins 85 and 86 mounted eccentrically in rotary disks 8'! and 88 on shafts B9 and 90. These shafts have bevel gear connections 9| and 92 with a drive shaft 93 mounted on brackets 94 and 95 secured to bracket 8|. -A gear 96 on shaft 93 is driven by chain 91 (Fig. '7) from aspeed control mechanism 98 driven by motor 99. The above construction does not provide for any vertical movement of the teeth with'respect to the felt, but the lateral motion from the eccentric drive lets stock pass at different and shifting points. The eccentric drive also gives the teeth more and less motion with respect to the passing stock, the teeth sometimes moving with the stock, and

sometimes moving against it. Vertical adjustment of the device or parts thereof may be readily effected, but for set production the depth need not be changed. The speed of the device can be so regulated that there are points where the blade moves with a longitudinal component at the same speed as the felt. As the teeth go slower than the stock, the stock is piled on the head-box side of the tooth. As a tooth goes faster than the felt in the felt-direction, the stock is piled on the discharge-end side of the tooth. Various patterns may thus be created.

Other forms of disturbing means are shown in Figs. 10 to 13. These comprise a drag device which rests by gravity on the moving felt F and by friction causes some of it to be held back. The drag may be a single rigid piece, a plurality of rigid pieces or a flexible piece. Only irregular patterns are possible since there is no mechanical control.

To illustrate these devices portions of the machine above described are shown'in Figs. 10 to 13, and the parts already described are numbered in accordance with the previous description. The parallel rails I and IN are positionedat a lower level. Brackets I02 and I03 are mounted adjustably longitudinally of the rails, and are connected by a fixed shaft I04 which is used as a pivotal mounting means for drag devices. Flat board-like elements (5 in number) I05 are mounted pivotally at one edge to the shaft I04, and have their opposite edges in position to drag on the surface of felt F. In action, these drag devices merely bump along on the surface when tion the invention may be readily understood. The means employed are only exemplary devices, subject to modification and change, to obtain the desired effect, as will appear from the nature of the invention defined in the appended claims.

I claim:

1. The method of making artificial board in the form of substantially rigid thick felted fiber sheets with special surface characteristics which comprises forming a felt on a screen from a uniform aqueous slurry of pulp, including dewatering the pulp through the screen whereby the felt formation is initiated, and disturbing the top layer of the felt by displacing portions of the partially dewatered pulp slightly to produce permanent variations in thickness of the felt as hills and valleys therein, the disturbance of the felt being such as not to destroy the original felted character of the bottom layer of the felt and such as not to destroy a felted relation between the displaced portions and the bottom layer, then further dewatering the felt, and drying the resulting sheet to form a flat rigid board while simultaneously pressing the high spots to the same level, whereby the treated surface is uneven and the sheet has a uniform caliper.

2. In the process of continuously felting fibers into a sheet, the steps of flowing a thin slurry of fibers onto a moving screen whereby to attain uniformity in a thick felt formation, then after partial dewatering of: the thick felt to a point where the same ceases to flow as a liquid and before the same has-set, disturbing the upper layer of the felt to vary its thickness locally in hilland-dale formation, said disturbance being conducted so as to avoid disturbing the lower layer and so as to avoid destroying a felted relation between the disturbed portions of the upper layer and the lower layer, then further dewatering the felt, and drying the resulting sheet to form a flat rigid board while simultaneously pressing the high spots to the same level, whereby the treated surface is uneven and the sheet has a uniform caliper.

' ORCUTT W. FROST.

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