US2703533A - Apparatus for treating paper stock - Google Patents

Description

March 8, 1955 E. cowLEs 2,703,533

APPARATUS FOR TREATING PAPERv s'rocx Filed April s, 1952 5 sheets-sheet 1 s 1o 15 2o 25 30 35 aw/,7 Bw/e5 ATTORNEYS AMarch 8, 1955 E. cowLEs APPARATUS PoR TREATING PAPER sTocx Filed April 3, 1952 5 Sheets-Sheet 2 INVEN-ron faw//l Cow/es BY 47,247@ 2P ATTORNEYS March 8, 1955 E. cowLEs APPARATUS FOR TREATING PAPER STOCK 5 Sheets-Sheet 3 Filed April 3, 1952 INVENTOR.

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ATTORNEYS March 8, 1955 E. cowLEs 2,703,533

APPARATUS PoR TREATING PAPER sfrocx Filed April 5, 1952 s sheets-sheet 4 HryT/o ATTORNEYS March 8, 1955 E. COWLES APPARATUS FOR TREATING PAPER. STOCK Filed April 3. 1952 5 Sheets-Sheet 5 ATTORNEY United States Patent O 2,703,533 APPARATUS FOR TREATING PAPER STOCK. Edwin Cowles, Cayuga, N. Y., assignor to The Cowes Company, Princeton, N. J., a corporation of New Jersey Application April 3, 1952, Serial No. 280,256 12 Claims. (Cl. 92-26) This invention relates to apparatus for treating paper stock.

This application is filed as a continuation in part of my copending applications Serial No. 137,743, tiled January l0, 1950, and Serial No. 252,930, filed October 24. 1951, both now abandoned.

ln the preparation of paper stock for delivery to a paper making machine, it is desirable, in most cases. to subject the stock to three types of action, ("1) a pulping and debering action to separate the individual fibers one from another, (2) a hydrating and fbrillating action which brushes and frays the fibers while at the same time causing them to absorb water, and (3) a cutting action to reduce the fibers to the desired length. It is necessary to completely defiber the stock inall cases, but in making certain types of paper, the cutting action or the hydrating and fibrillating action may be minimized, and one type of action may be caused to predominate over the other. ln fact, one of the skills of the paper making art is the ability to prescribe and obtain the type and degree of action required to produce paper of the desired properties and characteristics. 4

lt is an object of the present invention to provide apparatus which is capable of producing an unusual degree and type of fibrillating action, thereby producing an unusual strength development in the finished sheet. I

It is a further object of the invention to provide apparatus in which this unusual degree and type of fibrillating action can be produced in less time and with the consumption of less power than is ordinarily required to produce a lesser action.

It is a further object of the invention to provideapparatus in which this unusual degree and type of fibrillating action may be produced with a minimum of concomitant cutting of the fibers, thus permitting great strength development with only very slight accompanying loss in tear strength.

lt is a further object of the invention to provide apparatus which may be easily and quickly adjusted to produce an action which is either predominantly a hydrating and fibrillating action, or which is predominantly a cutting action.

It is a further object of the invention to provide apparatus in which a highly eicient defibering action always accompanies the refining action of the apparatus irrespective of whether the apparatus is adjusted for hydration and fibrillations or for cutting. This defibering action is accomplished without any substantial increase in the power consumption required to hydrate, fibrillate and cut the stock.

Finally, therefore, it is an object of the invention to provide apparatus which will accept raw, undefibered stock, and in which such stock may be defibered, and may be simultaneously hydrated, tibrillated and/or cut as desired by the operator, with power consumption which does not exceed that which could be required to produce comparable hydration, fibrillation and/or cutting alone in the same apparatus, and with power consumption substantially less than required to produce comparable hydration, fibrillation and/or cutting alone in refining apparatus such as a Hollander beater or a Jordan engine of the prior art.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawings, in which,

Figure 1 is top plan view of the apparatus.

Figure 2 is a vertical section on the line 2 2 of Figure 1.

Figure 3 is an enlarged view of the front face of the.

rotor and bedplate.

Figure 4 is a vertical section on the line 4 4 of Figure 2.

Figure 5 is a section on the line 5 5 of Figure 4.

, Figure 6 is a front elevation of a knife.

Figures 7, 8 and 9 are sections through the knife on the lines 7 7, 8 8 and 9 9 of Figure 6.

Figures 10, l1 and 12 are similar sections through a knife of modified form.I

Figure 13 is a section on the line 13 13 of Figure 2.

Figure 14 is a diagram showing typical results obtained by the use of this apparatus while maintaining constant pressure between the knives and bedplate.

Figure 15 is a similar diagram showing typical results obtained when pressures are increased during the treatment of the stock.

Referring to the drawings, the operating unit (apart from the container, tank or enclosure in which it is mounted) is shown in detail in Figures 3, 4 and 5, and comprises a bedplate 1 and a rotor 2 carrying knives 3. In the preferred embodiment illustrated, the bedplate is in the form of an annular ring having a working surface provided with a multiplicity of alternating grooves 4 and bars or lands 5.

The rotor 2 is mounted on shaft 6 for rotation therewith. The tangs 7 of knives 3 are clamped firmly to the rotor 2 by a ring 8 having bolts 9 extending through the tangs and into the rotor. The knives extend outwardly from the rotor and are in contact with the bars 5 of the bedplate. It is preferred that the leading edges of the knives 3 should engage the bars and grooves of the bedplate at a slight angle, and accordingly in the `embodiment illustrated in which the bars and grooves are arranged substantially radially, the knives are set so that the leading edges cross the bars and grooves at an angle between 10 and 30.

The knives are so constructed that during the operation of the machine the motion of the knives relative to the bedplate produces a hydraulic reaction which holds the knives in yielding contact with the.bedplate. Referring to Figures 6, 7, 8 and 9, it will be observed that the under surface of each knife is recessed at 10, leaving only a relatively narrowfoot 11 extending along the leading edge and in contact with the bedplate bars. As shown in these figures, the upper surface l2 of the knife, immediately adjacent the advancing edge 13 intersects the bottom surface of the foot at a relatively small angle, preferably less than forty-five degrees, which has been found to be a favorable angle for causing fibers to be picked up and retained on the advancing edge. Preferably the advancing edge of the knife is rather sharp and if the metal of the surface 12 s hardened, the knife will tend to be self sharpening in use. The remainder of the upper surface 14 is curved smoothly and intersects the surface 10 to form the trailing edge 15 of the knife. The knife is tapered toward its outer tip, resulting in cross sections of progressively decreasing area as shown in Figures 7, 8 and 9. In all sections, however, the width of the knife is substantially greater than its thickness.

A modified form of knife 3l is shown in Figures l0, 11 and 12 which would show slightly better hydraulic efficiency, but which would be more fragile and more costly. The form shown in Figures 7, 8 and 9 represents a practical departure from the theoretically more efficient form of Figures 10, l1 and 12 made in the interest of added strength and decreased cost. In both forms, the motion of the knives relative to the bedplate produces a hydraulic reaction having two distinct aspects. First, a region of reduced pressure is created within the space 16 between the surface 10 and the bedplate which tends to draw the two together to hold the knives in yielding contact with the bedplate. Second, the motion of the knives causes the stock to exert a downward pressure on the upper surface of the knife. The combination of reduced pressure on the under side of the knife and increased pressure on the upper side is particularly effective in maintaining yielding contact near the outer tip of the knife due to the fact that in practice the tip of the knife is moving at a relatively high speed, as for example at 3000' per min. or more. It is also particularly important near the outer tip of the knife for the knife is not completely rigid and has a tendency to flex. The

combination of hydraulic pressures aids in maintaining effective contact throughout the length of the knife.

lt is desirable that the bedplate and the rotor be mounted for relative axial movement, and in the embodiment illustrated, the rotor is fixed in its bearing housing but the bedplate is movable axially relative to the rotor. Thus the bedplate is mounted on three push rods 17 which are mounted in and guided by sleeves 18. Said rods are connected to a collar 19 which, in turn, is connected to three hydraulic cylinders 20.. Said cylinders are connected to a source of hydraulic pressure by pipes 21 having a pressure regulator 22 therein through ,which the pressure in the cylinders may be controlled.

A rubber gasket 23 may be interposed between the bedplate and the casing. Since the bedplate of the embodiment illustrated is a closed bedplate (having no slots or apertures extending therethrough) the reduced pressures within the spaces 16 under the blades tend to draw the bedplate toward the knives and to hold it against the knives with a yielding pressure of some magnitude. This pressure may be increased (or decreased if desired) by varying the pressure applied to the cylinders 20.

The nature of the refining action on the fibers, that is, whether a hydrating and fibrillating action predominates or whether a cutting action predominates, is determined primarily by the pressure between the knives and the bars of the bedplate. In general, even when using rather sharp knives, when light or moderate pressures are applied, as when the hydraulic reaction above described are relied upon alone, or when such hydraulic reactions are supplemented by moderate additional pressures from the cylinders, a hydrating and fibrillating action will predominate with little or no cutting of the fibers. If, however, pressures are increased substantially, and even assuming no change in the sharpness of the knives, a cutting action will predominate. Increased sharpness of knives will, of course, increase somewhat the cutting effect obtained at any given pressure.

The nature of the refining action is inuenced importantly by the spacing between successive bars of the bedplate. It will be understood that the wider the spacing between successive bars, the further a knife must move between successive engagements, and the greater the opportunity for the knife to pick up fibers. Thus, if the spacing between successive bars (i. e. groove width) is l, a knife would be likely to pick up twice as many fibers as if the spacing was y As a result of extended experimentation and close observation of such machines under various conditions, I am convinced that the very unusual results which have been recorded as to extraordinary strength development (tensile and Mullen burst test) accompanied by unusually low loss of freeness and unusually low loss of tear strength, are due in large part to the use of a bedplate in which the bars are very closely spaced. If the spacing between successive bars (i. e. groove width) is less than 1/2" it appears that at ordinary operating stock consistencies of 4% to 6% a knife tends to pick up only a few fibers constituting more or less a single layer of fibers, while at spacings greater than this, a pad4 of fibers is likely to be accumulated. With only a few fibers it appears that subsequent engagement with a bar causes the individual fibers to be dragged across the edges of the knife causing the walls and ends of each fiber to be torn and frayed, whereas with an accumulation of sufficient fibers to form a pad, it appears that some of the fibers are protected from such fraying action. In any event, I have observed that with increased bar spacing the loss of tear strength is more pronounced, and the development of tensile and burst strength (Mullen) proceeds more slowly. I prefer to limit the space between the bars, therefore, to l/" or less, for in this way I obtain results which it is difficult, if not impossible, to duplicate in any existing apparatus.

l have obtained excellent results with a bedplate in which the distance between adjacent bars (groove width) is 366". In this bedplate, as illustrated in Figures 7 to l2 inclusive, the depth of' the grooves is 1;/4" and the width of the bars varies from %5" at their inner ends to 1A" at their outer ends. However, the depth of the grooves and the width of the bars do not appear to have important significance, as it appears to be the groove width alone which affects the character of the results on the bers.

The unusual results obtained in my machine are shown in Figures 14 and l5 showing curves plotted from tests on pulp treated in my machine.

The pulp selected for the test.recorded in Figure I4 was a bleached Tacoma kraft pulp `in water at 68 F. at a consistency of 4.5%. The entire charge of pulp was introduced in to the machine in the form of air dry sheets at the beginning of the run. Samples were taken at regular intervals and tested by accepted standard procedures. The results are plotted in terms of horsepower per ton per day.

During the test, the pressure between the knives and bedplate was constant and relatively low, the pressures induced by the hydraulic reaction of the knives being only slightly supplemented by pressure applied by the hydraulic cylinders. During the operation of themachine, the stock was defibered as well as hydrated and fibrillated, but because of the low pressures between the knives and bedplate, there was very little cutting. The curves indicate a moderate but steady increase in Mullen strength which was still increasing at 35 horsepower per ton per day when the test was discontinued. This was accompanied by a rapid increase in tear strength up to about l2 horsepower per ton per day, followed by a relatively slow decrease in tear strength. Simultaneously, a gradual and relatively slow drop in freeness was observed.

Ordinarily, a paper maker would discontinue treatment far short of 35 horsepower per ton per day, and the significance of the results shown by these curves is that for any given Mullen strength which may be required, stock treated in my machine will in almost every case show a higher tear strength and a smaller drop in freeness than will the same stock treated in standard equipment such as a Hollander beater or a Jordan engine to obtain a Mullen strength of equal value. For example, a similar stock treated in a Hollander beater to produce a Mullen strength of 80% (reached in my machine at l5 horsepower per ton per day) would show lower tear strength and a greater freeness drop than those here recorded.

The pulp selected for the test recorded in Figure l5 was a Weyerhaeuser Standard Bleached Sulphite Pulp in water at F. at a consistency of 5%. Again the entire charge of pulp was introduced into the machine at the beginning of the run in the form of air dry sheets. Samples were taken and the results plotted in the same manner as before.

In this test, the pressure between the knives and bedplate was increased greatly at approximately 9.5 horsepower per ton per day, the outside pressure applied by the hydrauliccylinders having been increased from approximately 6 lbs. per square inch to approximately 50 lbs. per square inch 'at this point. The effects of the increased pressure are shown graphically in the curves. Thus, the tensile curve turns upwardly quite sharply and the Mullen curve also turns upwardly, but less sharply. On the other hand the tear curve and the freeness curve,

' both of which were tending to level off at 9.5 horsepower per ton per day, again turn downwardly. This test was discontinued at 25 horsepower per ton per day, but the qualities shown by these tests at any value between l0 and 25 horsepower per ton per day are unique in their high Mullen and tensile strengths with the accompanying tear and freeness readings. These qualities are often sought but have seldom been achieved. They are believed to be largely due to the unusual type and degree of fibrillation which is obtained in the ordinary use of my machine with relatively sharp knives.

In making certain types of paper, however, greater hydration and less fibrillation is sometimes required. In such cases, this may be accomplished in my machine merely by using knives having a dull rather than a sharp advancing edge. In such case, there is less tendency to fray the fibers and more tendency to crush and pound them. Preferably, however, the machine is equipped and adjusted as previously described.

The importance of these results is further increased by the fact that in these tests the pulp was supplied in the form of air dry pulp sheets. Ordinarily the defibering treatment of the stock required to prepare it for refining treatment would require the expenditure of approximately 2 to 5 additional horsepower per ton per day, whereas in my machine debering proceeds coincidentally with the refining.

The detibering action in my machine is extremely efcient although its exact nature is not yet completely understood. It is believed to' result from a combination of mechanical and hydraulic forces working on the Undoubtedly some defibering results from the direct mechanical action of the -knives working against the bedplate. Then again, an area of extreme turbulence exists in the spaces 16 beneath the knives which probably produces a combined hydraulic and mechanical deliberng action therein. This would be augmented, no doubt, by an area of turbulence lying immediately behind the trailing edge 15 of each knife in which a hydraulic deibering action might be irected. It suffices vto say that the delibering action is s ciently rapid and ellicien't to be completed prior to the time when the required rening action has been completed, and with no appreciable increase in power consumption. That is, the results obtained after expenditure of any given amount of power will be substantially the same irrespective of whether the pulp is supplied in the form of dry sheets, or in par'- tially or completely defibered form.

In the preferred embodiment illustrated, therefore, the operating unitpreviously described is shown as mounted in a tank capable of receiving raw, dry pulp, for important savings, not only in power but in time, can be achieved by thus making it possible for deibering and refining to proceed simultaneously. Thus, the operating unit, including the shaft bearing housing 25 and the hydraulic cylinders 20, both of which are connected to plate 26, is mounted on the at side wall 27 of the tank 28 with the bedplate and knives freely exposed to the contents of the tank.

The tank is of modified cylindrical contour in which the at side wall 27 is tangent to a curved wall section 29 which merges with another curved section 30 of somewhat longer radius. The latter meets and joins the wall 27 to form a corner 31. The operating unit is located near this corner.

Rotation of the rotor causes stock to be discharged outwardly in all directions'from the axis of rotation, and in order to control the discharge to produce adequate circulation of the stock in the tank, the rotor is partially surl rounded by a casing 32, preferably of volute form which intercepts and redirects the stock discharged from a portion of the rotor to cause it to move in the general direction of the stock discharged from the -remainder of the rotor. The resulting circulation is somewhat as indicated by the arrows in Figures 1 and 2. A portion of the stock is permitted to discharge substantially vertically upwardly, as indicated, to be intercepted and dellected by the baille 33 to aid in submerging any pieces of stock which tend to oat on the surface. The bottom portion 34 of the casing 32 may be provided with apertures 3.5 through which finished stock may be extracted. The exterior portion of casing 32 is surrounded by an outescasing 36 having a sump 37 and an outlet opening If desired, the circulating action of the rotor may be increased by mounting a series of .vanes 39 on the ring 8, said vanes being inclined to the radius, as shown, to

assist the normal outward discharge from the blades. A.

vane 39 on the shaft 6 may also be used to assist circulation, and particularly to break up accumulations of pulp around the center of the rotor. Such vanes assist in delibering undebered stockbut have no appreciable tecbin producing either fibrillation or shortening of e ers.

In the normal operation of the machine, the desired4 quantity of water will be introduced and the necessary quantity of pulp will then be introduced to produce the desired stock consistency. In most cases, a consistency of 4% to 6% will be advisable. One of the advantages of the machine is its ability to receive an entire charge of dry pulp at one time. Whole bales of dry pulp may be introduced without separation of individual sheets or laps. In the preferred method of operation where it is desired to effect maximum strength development, the machine is then operated with the knives first exerting relatively light pressure against the bedplate. Subsequently, at a point which will be determined by the l. qualities desired, increased pressure is applied topproduce suicient cutting for good sheet formation.

It will be understood that the invention may be variously modified and embodied Within the scope of the subjoined claims.

I claim as my invention: l. Apparatus for treating paper stock comprising, in

' combination, a bedplate having a working surface comprising spaced bars, a rotor mounted concentrically of said bedplate, a knife carried by said rotor, said knife `engaging the bars of the bedplate, said trailing edge bein g located above and out of contact with said bedplate, said knife beingrecessed behind said foot and between said foot and said trailing edge to form a space between the knife and the bedplate.

2. Apparatus as claimed in claim l in which said knife is somewhat flexible and in which one end of the knife is free and the hydraulic reaction of the knife on the stock causes said knife to flex and to exert yielding pressure on said bedplate.

3. Apparatus as claimed in claim 1 in which said leading edge is formed by surfaces which intersect at an angle of less than 45 4. Apparatus as claimed in claim l in which said bedplate and rotor are relatively movable in a direction parallel to the axis of rotation of the rotor, and in which the hydraulic reaction produced by rotation of said rotor exerts yielding pressure between the rotor and bedplate.

5. Apparatus as claimed in claim l in which said bedplate is closed and is mounted for movement parallel to the axis of rotation of the rotor, and in which the hydraulic reaction produced by rotation of said rotor causes said bedplate to exert yielding pressure against said rotor.

6. Apparatus as claimed in claim 1 in which said bedplate and rotor are relatively movable in a direction parallel to the axis of rotation of the rotor, and in which means are provided for applying variable yielding pressure therebetween.

7. Apparatus as claimed in claim l in which said bedplate and rotor are relatively movable in a direction parallel to the axis of rotation of the rotor, and in which the hydraulic reaction produced by rotation of said rotor exerts yielding pressure between said rotor and bedplate, and in which means are provided for applying supplemental variable yielding pressure therebetween.

8. Apparatus as claimed in claim l in which said bedplate is closed and is in the form of a disk and in which grooves between the bars extend radially outwardly from the center of said disk.

9. Apparatus as claimed in claim l in which the spaces between successive bars are less than'l/" in width.

l0. Apparatus as claimed in claim 1 in which said bedplate is mounted in the wall of a tank adapted to receive raw, undebered stock, with the working surface of said bedplate and said knives freely exposed to the contents of the tank.

1l. Apparatus as claimed in claim-l in which said bedplate is mounted in the wall of a tank adapted to receive raw, undefbered stock, with the working surface of said bedplate and said knives freely exposed to the contents of the tank, and vanes on said rotor to supplement the normal outward discharge of stock from said rotor.-

l2. In an apparatus for treating paper stock, a knife comprising a blade'and a tang, said tang extending lengthwise from said blade at one end thereof, said blade having a leading edge and a free trailing edge, said leading edge being formed by the intersection of two surfaces, one of said surfaces constituting the bottom surface of a relatively narrow footy/ extending along said leading edge, the bottom of said blade being recessed behind said foot and between said foot and said trailing edge, the upper surface of said blade being smoothly and convexly curved from said foot to said trailing edge, and said trailing edge lying above the plane of the bottom vsurface of said foot.

References Cited in the file of this patent UNITED STATES PATENTS 232,460 Cooke et al. Sept. 21, 1880 2,220,677 Cowles Nov. 5, 1940 2,399,988 Cowles May 7, 1946 2,527,772 Stapley et al. Oct. 31, 1950 2,561,013 Coghill et a1. July 17, 1951 FOREIGN PATENTS 262,070 Great Britain May 19, 1927

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