US2847913A - Stock inlet system for a paper making machine - Google Patents

Description

Au 19, 1958 A. J. CIRRITO 2,847,913

STOCK INLET SYSTEM FOR A PAPER MAKING MACHINE Filed Feb. '7, 195s 3 Sheets-Sheet 1 INVENTOR.

ATTORNEY A. J. damn-o Aug. 19, 1958 STOCK INLET'SYSTEM FOR A PAPER MAKING MACHINE Filed Feb. 7, 1956 3 Sheets-Sheet 2 INVENTOR. Anthony 1' C'z'rrzzo ATTORNEY A. J. CIRRITO STOCK INLET SYSTEM FOR A PAPER MAKING MACHINE 3 Sheets-Sheet 3 Uni AW b0 Tfroz Filed Feb. 7, 1956 L A .u 2013 om mm MM W C l V: m h f n A A TTORNE Y United States Patent STOCK INLET SYSTEM FOR A PAPER MAKING MACHINE Anthony J. Cirrito, Shrewsbury, Mass assignor to Rice Barton Corporation, Worcester, Mass., a corporation of Massachusetts Application February 7, 1956, Serial No. 563,934

7 Claims. (CI. 92-44) This invention relates to a paper making machine and, more particularly, to that portion of such a machine, referred to herein as the stock inlet system, which feeds the dilute paper stock from a source of stock supply to the head box (or similar element) for subsequent distribution onto a forming wire or cylinder.

Needless to say, the desired end result of any paper making machine (and process) is a paper product of even and uniform thickness. To this end, it is essential that the stream of stock flowing onto the forming wire or cylinder (at the slice, for example) should have a like uniform distribution of fibers across the width of the wire or cylinder. For several reasons, as will appear hereinafter, it is very difiicult to achieve such a uniform distribution.

Some small measure of this distribution problem may possibly be reflected in the various irregularities found in the head box, or other element, immediately preceding the slice; principally, however, the distribution problem makes itself manifest in the inlet or supply system which feeds the stock to the head box, or the like element. Briefly stated, the essentials of this inlet system involve the conversion of a stream of dilute paper stock flowing in a large round pipe into a thin flat ribbon-like stream of a width many times thediameter of said pipe. Thus, while the flowing stock stream is undergoing this change in shape, it is important that a uniform distribution of fibers in the stream be achieved and maintained.

In the past many proposals have been put forth in an attempt to solve this distribution problem. One of the common practices has involved a subdivision of the stock stream from the main supply into a plurality of equal and parallel paths leading into the head box. Each path is designed to change the flow into a flat stream at its outlet end; the outlets of all paths are then combined into a single flat stream whose total width is that of the forming wire, which combined stream is then fed into the head box. This design is an attempt at a perfect geometric arrangement in which volumes of flow, as Well as the flow resistances, in all'paths of flow from the supply pump to .the head box are theoretically equal. In practice, this perfection has been impossible to achieve to the extent that actual arrangements of this nature have proved unreliable and therefore unsatisfactory in actual operation. In this invention, as will appear hereinafter, this inherent imperfection has been recognized, and as a result, flow meters and control valves have been incorporatedin each parallel flow path to insure equal flow by a means independent of the geometry of the system.

Therefore, it is a principal object of this invention to provide an inlet for supplying paper stock to a paper machine under controlled conditions of substantially uniform velocity and fiber distribution across the width of the machine so as to impart like uniformity to the sheet or web being manufactured. I

Another object of this invention is to provide a stock inlet system which may be applied to a Fourdrinier or cylinder type of paper machine for use with anytype of head box, such as an open head box, a closed or pressure type head box, or an air dome head box, or with a flow distributor for the cylinder type of machine.

A further object of this invention is to provide a stock inlet distributor consisting of a multiplicity of substantially identical parallel sections, with the dimensions of of separate elements representing incremental values of total machine Width.

A further object of this invention is to provide a stock inlet system in which energy losses are held to a minimum, thus reducing the development of large scale turbulence with accompanying flow instabilities, which instabilities are ultimately reflected in a poor or non-uniform distribution of stock at the web-forming portion of the paper machine.

A further object of this invention is to provide a stock,

inlet system of the type referred to above wherein the operation of said system is independent of the total vol. ume of paper stock flowing through the system.

Other and further objects and advantageous features of this invention will hereinafter more fully appear in connection with a detailed description of the drawings in which Fig. 1 is a front view of a stock inlet system, according to a preferred embodiment of this invention. 7 Fig. 2 is a sectional view taken along the section line 2-2 of Fig. 1, showing the details of one of the several identical flow paths. I Fig. 3 is a sectional view taken along section line 3 3 of Fig. 2, showing how the flow spreaders are connected to the headbox.

Fig. 4 is a diagrammatic view showing the control circuits used with the arrangements of Figs. 1 and 2.

Fig. 5 is a graphical representation of the velocity dis tribution across the discharge ends of the flow spreaders. Fig. 6 is a diagrammatic view similar to Fig. 4 illustrating another modification of this invention. V Fig. 7 is a diagrammatic view similar to Figs. 4 and 6 illustrating a further modification of this invention.

In Fig. l, which illustrates the preferred embodiment of this invention, there is shown a head box 1 which may be one of several conventional types and which forms no part of this invention.

paper stock is provided for the head box 1 by means of supply pipe 2, pump 3, manifold 4, branch pipes 5 and flow spreaders 8, all of which will be later described in greater detail. Supply pipe 2 is connected to a source of constant head such as a de-aerating device (not shown) or a stock preparation tank (not shown) for supplying a flow of. paper stock of a consistency suitable for delivery to the web-forming zone of the paper machine.

The paper stock flowing in pipe 2 passes into pump 3, which,.in the. preferred embodiment of this invention,

is driven by a variable speed motor 11 (shown symboli' cally in Fig. 4), which drive may be accurately controlled as to its speed. Other pumping systems apart from those illustrated herein might be employed for the purpose of creating a supply of paper stock under pressure; for example, a constant speed motor and pump might be used in conjunction with a throttling valve to vary the pressure and volume of flow; also, such a con- Patented Aug. 19, 1958 (As shown in this' view and in Fig. 2, however, the head box is of the well-known closed or pressure type.) A flow of dilute 3 stant speed motor and pump with a variable bypass might be used for the same purpose; finally, it is possible to produce this source of pressure without using any pump at all, by means of an elevated weir, or the like, and a connecting standpipe, in which case the head of liquid alone would produce the desired pressure.

Returning to Fig. 1, the pump 3 discharges the paper stock into a cross-flow manifold 4 to which the branch pipes 5 are connected. The shape of this manifold is tapered relative to the positions and number of branch pipes 5 in such a manner that the velocity of the stock flow at any portion of the manifold is substantially constant. Also, the shape of the manifold is sutficiently streamlined so that, when the stock is flowing at the desired velocity, any difliculties due to settlement of stock will be eliminated. For the sake of simplicity, only three branch pipes 5 are illustrated in Fig. l, but it should be understood that a greater number of branch pipes might be employed, particularly where the forming wire is considerably wider. Naturally, when more than three such pipes are used, a longer manifold, constructed in a similar fashion to that illustrated in Fig. 1, would be employed.

For the purpose of connecting the branch pipes 5 to the manifold 4, three offtake portions 4a, 4b and 4c are provided. At their lowermost points of connection to the manifold 4, these otftakes are curved in the forward direction of flow to minimize unwanted turbulence. Also, each of the branch pipes 5, within the limits of practical design and construction, is the same in cross-sectional area, with said area being substantially circular. This design would provide a theoretically equal flow of liquid through each of the pipes 5; however, realizing the practical shortcomings of any attempt to achieve such an ideal condition, this invention provides means for measuring and compensating for flow variations between the several branch pipes 5. In each branch pipe 5, the measuring and compensating means referred to above consist of a control valve 6 for permitting minor flow adjustments and a flow meter 7 for accurately measuring the rate of flow. The position of each control valve 6 may be varied manually in accordance with the indication of its respective flow meter 7 to provide exactly equal flow in all branch pipes 5. Preferably, however, and as shown diagrammatically in Fig. 4, an automatic controller 10, pre-set at a given control point, coordinates the reading of each flow meter with its corresponding control valve so as to provide a constant even flow in each pipe 5, thus eliminating the need for manual control.

Each control valve 6 is preferably of the butterfly type, with the disc portion 6a of the valve being relatively thin so as to provide little or no resistance to the flow stream. As best shown in Fig. 2 each control valve 6 includes a disc-shaped vane 6a centrally mounted on a rotatable supporting rod 612. A pneumatic valve positioner (not shown) operatively associated with each controller 10 and the rod 61) of the corresponding valve 6 will accurately position the vane 6a for the proper fiow condition in each branch pipe 5. It is felt that this type of valve can provide the required minor variations in flow without adding any appreciable resistance or undue turbulence. However, other valves having like properties, i. e. the property of minimizing unwanted turbulence, may be employed for the same purpose.

Each flow meter 7, as employed in its corresponding branch pipe 5, may be one of several non-resistant types. As far as the overall invention is concerned, it is important that these meters provide an accurate measure of flow without adding any appreciable resistance to the flow itself. The particular meters per se form no part of this invention except as they are associated with the other elements of the general combination. However, to aid in a better understanding of the invention, the meters 7 shown diagrammatically in Figs. 2 and 4 are substantially of the construction and principle of operation disclosed by Coulter Patent No. 2,733,604, dated February 7, 1956. Between the outer casing 7a and the inner pipe section 711 of each flow meter 7, appropriate electrical coils (not shown) are situated. When a current of electricity passes through these coils, a magnetic field will be set up across the pipe section 71). The inner surface of the latter pipe section is suitably lined with insulating material (not shown) such as neoprene or the like; as an alternative, the pipe section 7b may be constructed of some non-conductive material such as Transite. A pair of electrodes 7c and 7d, suitably insulated from the pipe section 7b, are fastened in the wall of the tube 7b in positions opposite to one another. A pair of lead wires 7e and 7 connect the electrodes to the controller 10. Now, as the stock flows within the pipe section 7b, it will cut across the magnetic lines of force of the magnetic field thus setting up a voltage diiference between electrodes and 7d. This voltage difference will increase or decrease as the rate of flow of stock increases or decreases, respectively. Therefore, this voltage difference can be used as a measure of the rate of stock flow through the meter 7. Although the type of flow meter described above is relatively new in the field of measurement and control, nevertheless, as explained above, it forms no part of the invention except as it is associated with the other elements of the disclosed combination. Furthermore, other flow meters, such as those of the Venturi type, which offer little resistance to the flow stream can be used in place of the above described magnetic flow meters.

Each controller 10 is adjusted and properly calibrated for converting the voltage difference supplied by the leads 7e and 7 into a corresponding value of flow, such as in feet per second. Also, each controller is equipped with a pneumatic control circuit (not shown) for supplying pneumatic pressure to the pneumatic valve positioner in accordance with any indicated deviation from a predetermined and preset control point. The coordinated activities of the flow meter 7, the controller 10, and the valve 6 will hold the flow in each branch pipe 5 at a steady constant rate. The measurement and control devices herein shown need not be illustrated or described in any greater detail because such devices per se are well known, and because other measurement and control devices utilizing well known electrical and/or hydraulic principles might be equally well adapted for use with the apparatus of this invention.

At the upper end of each branch pipe 5, beyond the meter 7, a flow spreader 8 is connected for changing the cross-sectional shape of the flow. stream from circular to that of an elongated rectangle. Accordingly, the lower end of each flow spreader 8 is circular and of the same cross-sectional area as branch pipe 5; the upper end of each flow spreader 8 is also equal in cross-sectional area to that of the branch pipe, although the shape has been changed to an elongated rectangle. Thus, as the flow stream changes its shape in spreading out, there is no change in the overall velocity since the cross-sectional area is constant. Figs. 1 to 3 inclusive best show the details of the flow spreader 8.

As shown in Figs. 1 and 3, the divergent shape of the flow spreaders (in a direction across the machine width) will cause the How stream to increase in width; as shown in Fig. 2, the convergent shape of the flow spreaders (in a direction at right angles to the machine width) will cause the flow stream to decrease in thick ness. The angle of divergence 0 shown in Fig. 3 is limited in magnitude to that degree where the fluid begins to separate from the side walls, imparting undesirable channeling to the flow stream. Satisfactory results have been obtained where the angle 0 is of the order of 12 degrees.

As explained above only three parallel flow paths have been shown in the drawings, this being for purposes of simplification. In actual practice, aspac'ing of about 2 feet between the centers of the flow paths has been employed advantageously. The total machine Width (or slice width) of the apparatus shown in Fig. 1 would be about 6 feet if the same spacing were utilized. On a 16 foot machine, therefore, eight flow paths would be used, with eight branches 5, 5 from supply manifold 4, and eight flow spreaders 8, 8 for conecting said branches to the head box.

The several flow spreaders 8, 8 are so connected at their upper ends to each other and to the interior of head box 1, that the individual flat streams issuing from these flow spreaders are merged within the head box into a single flat stream whose total width is that of the head box or slice. Fig. 3 shows in detail how'these flow spreaders 8 (or transition pieces as they might be called) are connected to the head box. The flow spreaders are connected by welding or other suitable means to a flange strip 20 which encompasses the periphery of the flow spreader array. Also, this flange strip is provided with cross-members 21 which pass between the flow spreaders at their junctures and may be suitably welded thereto. The head box 1 is provided with a corresponding flange 22 to which the flange strip 20 is secured by means of threaded bolts 23. A suitable gasket (not shown) may be interposed between the flange portions as desired. Also, the head box 1 is provided with crossmembers 25 which extend across the flange portion 22 at positions corresponding to the cross-members 21. The latter cross-members are secured to their corresponding cross-members 25 by means of threaded bolts 23. As shown in Fig. 3, the cross-members 25 are appropriately tapered in the forward direction of flow to facilitate a smooth combination of the individual flow streams into a single flow stream.

Since the flow spreaders are substantially identical in size and shape, and since the aforementioned system for measurement and control will equalize exactly the flow conditions in the parellel flow streams, it would appear that the velocity across the combined flow stream (as fed into the head box) would be constant, and, essen tially, such is the case; however, at certain places in the combined flow stream corresponding to the junctures of the flow spreaders there is a slight reduction in the velocity head due to attenuation of the separate streams by the side walls of the flow spreaders.

Fig. 5 shows a graphical representation of the velocity distribution at the inlet to the head box; the velocity is indicated by the ordinate values, and corresponding values of width are located along the abscissa. The three identical portions of the curve represent the three flow spreaders employed in the arrangement of Fig. 1, and the width w of each portion represents the width of the corresponding flow spreader at its outlet end. The total width of the curve represents the width of the head box or slice. The flats of these curves are indicated by V and the lowest points of the depressions are indicated by V It should be apparent that each portion of the curve has the same V and V such that the variation in velocity is uniform across the width of the machine.

If a greater number of flow spreaders 8 were employed for a given Width of machine, the total variation in velocity (V would be correspondingly smaller than when a lesser number of flow spreaders were applied to the same machine. Satisfactory results have been achieved where one flow spreader is used for each 2 feet of machine width. In any event, these small velocity variations are evened out or dissipated when the 'flow stream passes through a cross-flow distributor roll 14 or similar resistance device located adjacent the inlet opening of the head box 1 as shown in Fig. 2. This distributor roll may be a hollow, perforated and rotatable roller which is commonly called a holey roll.

As shown in Fig. 2, the stock stream passes beyond the distributor roll 14' and into the main portion of the head box 1 which, as described above, can be any one of several well-known types. From the head box 1, the stock stream flows through a conventional slice 15 onto a suitable forming wire 13 which is directed around a breast roll 12 in a conventional manner.

In accordance with the introductory remarks contained herein, it should be apparent that the quality of the web so deposited on the forming wire 13 depends upon the quality of the stock stream fed to the head box 1, or similar distributing device. Accordingly, by means of this invention which provides a means for insuring uniformity of the stock stream across the entire width of the machine, the resulting paper web formed on the wire 13 will be uniform in thickness and in fiber distribution.

Fig. 6 represents a modification of Fig. 4 (or Fig. l) in which a separate variable speed pump 3 is used in conjunction with each branch pipe 5. As in the case of Fig. l, the sizes and shapes of branch pipes 5 and flow spreaders 3 are made uniform. The pumps in all flow paths are adjusted and preset by means of their respective motors- 11 to provide substantially equal flow in all flow paths. Again, in similar fashion to Figs. 1 and 4, the flow is made exactly equal by means of the coordinated activities of the valves 6, the flow meters 7 and the controllers 10.

Fig. 7 illustrates a further modification in which the valves 6 have been eliminated by virtue of a control system which varies the speed of the pumps 3. In this system a somewhat different type of controller 10' will be used to convert the voltage difference supplied by the meter 7 into a secondary voltage difference for controlling the ultimate speed of each variable speed motor 11/ It should be understood that any one of several different types of controllers 10 or 10' might be used in the several modifications described above in accordance with the well-known principles of flow measurement and control.

The essence of the invention disclosed herein involves a subdivision of the total stock stream into a plurality of individually controllable parallel flow paths each one of which represents a fraction of the total machine width. Optimum design dictates the use of one such flow path for approximately each 2 feet of machine width, although the flow paths could be considerably closer together. For different widths of machine, it is only necessary to vary the number of flow paths accordingly, and the same design of each flow path can be used regardless of the machine Width. Thus there is a uniformity in the application of this invention to diiferent sizes of paper machines; for example, with a 16 foot machine, eight flow paths and flow spreaders would be employed; for a 20 foot machine, ten flow paths would be used, and so on.

Again, it might be pointed out that the system of this invention is independent of the total quantity of stock flowing through this system. In other words, as far as Fig. 1 is concerned, if the speed of the pump 3 is varied to increase or decrease the rate of total stock flow, the rate of flow in the individual flow paths will still be equal by virtue of the instant design. Where the controllers 10 are employed for automatic control, it will be necessary to make corresponding changes in their mean control points for each different speed of the pump.

The foregoing observations have been based upon the assumption that the head box 1 (or its corresponding counterpart in a different type of machine) contributes nothing in the way of irregularities to the stock stream flowin therethrough; such an assumption can be considered as reasonable in view of the generally consistent results achieved by present-day head boxes. However, it sometimes happens that a given head box will impart irregularities to the flow stream, either in the box itself, or at the slice; also, it may be desirable in a few instances to change the thickness of the sheet slightly at a localized point across its width to compensate for irregularities at the dry end of the machine, such as in pressing or drying. In either of these two cases, it is possible to change the flow locally at the inlet to the head box by intentionally making the flow greater or lesser in one or more of the individual flow paths.

It should also be pointed out that the various elements in this invention have been designed to minimize energy losses in the system. The types of valves and meters employed have been selected to provide a minimum of resistance to the flowing stock stream. The bends and turns have been streamlined appropriately to minimize resistance and unwanted turbulence.

Other and further modifications apart from these described herein can be made within the spirit of this invention.

I claim:

1. Apparatus for supplying dilute paper stock to the distributing means for the slice of a paper making machine comprising means for feeding dilute paper stock from a source of supply of said stock to a plurality of parallel and confined flow paths whose cross-sectional areas are substantially of the same size and shape, a plurality of means connected to the discharge ends of said flow paths for spreading the resulting flow streams from said flow paths into a plurality of thin flat streams of the same width and thickness, said plurality of spreading means being arranged at their discharge ends in side-byside relation so as to combine the individual so-flattened streams into a single efiluent whose Width is substantially equal to that of the slice and Whose thickness is substan tially the same as the thickness of one of said individual so-flattened streams, a flow-varying means in each flow path, a flow meter in each flow path to accurately measure the rate of stock flow therethrough, and control means responsive to each flow meter for so influencing the associated flow-varying means as to maintain equal rates of stock flow in all of said flow paths.

2. The improvement as set forth in claim 1 wherein said stock feeding means comprises a pump connected at its inlet end to said supply, a manifold connected at its inlet end to the discharge end of said pump, and a plurality of discharge oiftakes from said manifold connected to the inlet ends of said flow paths, and wherein each of said flow varying means comprises an adjustable valve positioned in each flow path.

3. The improvement as set forth in claim 1 wherein said stock feeding means comprises a plurality of pumps, each of said pumps being connected at its discharge end to the inlet of each flow path, and means for connecting said supply to the inlet ends of said pumps in parallel, and wherein each of said flow varying means comprises an adjustable valve positioned in each flow path.

4. The improvement as set forth in claim 1 wherein said stock feeding means includes a plurality of variable speed pumps, each of said pumps having a discharge end connected to the inlet end of each of said How paths, and means for connecting said supply to the inlet ends of said pumps in parallel, and wherein each of said flow varying means comprises a means for varying the relative speed of each pump.

5. A stock inlet system for feeding a stream of dilute paper stock from a source of stock supply to a distributing means at the slice of a paper making machine comprising a plurality of fluid conducting conduits of substantially the same cross-sectional area and shape, means for causing said stock to flow under pressure from said stock supply to said conduits so that the volumetric flow in said conduits is substantially equal, a flow meter in each conduit, to accurately measure the rate of stock flow therethrough, a valve adjustable in each conduit to provide minor variations in said rate of stock flow, control means responsive to each flow meter for so influencing the associated valve as to maintain equal rates of stock flow in all of said conduits, and a flow spreader connected to the discharge end of each conduit for changing the cross-sectional shape of the stream flowing in each conduit to that of an elongated rectangle, said flow spreaders being substantially identical in size and shape and being connected at their discharge ends to said distributing means, said flow spreaders being also arranged at their discharge ends in side-by-side relation so as to combine the individual rectangular-shaped streams into a single rectangular-shaped stream Whose width is substantially the same as that of the slice.

6. The improvement as set forth in claim 5 wherein said means for causing said stock to flow from said supply to said conduits comprises a single pump connected at its inlet end to said supply, a manifold connected to the discharge end of said pump, said manifold being gradually and convergingly tapered in the forward direction of flow, and a plurality of fluid offtakes connected at their inlet ends to said manifold and at their outlet ends to the inlet ends of said conduits, the connections between said offtakes and said manifold being positioned relative to the tapered shape of said manifold to provide'a substantially constant rate of flow along the length of said manifold.

7. The improvement as set forth in claim 5 wherein said means for causing said stock to flow from said supply to said conduits comprises a plurality of variable speed pumps connected at their discharge ends to the inlet ends of said conduits, and a manifold having a plurality of discharge ofitakes connected to the inlets of said pumps and having an inlet connected to said supply.

References Cited in the file of this patent UNITED STATES PATENTS

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