US2393244A - Paper machine head box - Google Patents

Description

m 1946- P. H. GOLDSMITH 2,393,244

PAPER MACHINE HEADBOX Original Filed Sept. '27, 1938 2 Shee ts Sheet 1 INVENTOR Philip fiyoidlsmif/z Jan. 22, 1946.

, P. H. GOLDSMITH PAPER MACHINE HEADBOX Original" Filed Sept. 27. 19:3

2 Sheets-Sheet 2 miif l. WM?

8 M 0/. R v m N m mm A Y a Patented 22,1946

UNITED STATES PATENT orrice g fiififiilmfifx Original application September 21, was, Serial No. 231,854. Divided and this application May 9, 1941. Serial No. aaa'uc 10mm. -(Cl.9246) I mit subsequent removal of ll! and the establish- This invention relates to the art of paper makin and more particularly to an improved type of head-box for use in conjunction with a paper making machine. The present application is a division of my co-pending original application Serial No. 231,854, filed September 27, 1838.

In most paper making machines a sheet or web is formed by bringing a paper stock comprising a pulp suspension into contact with a foraminous forming'surface and permitting or causing the water of the pulp suspension to flow through the holes in the forming surface leaving a matted layer of fiber on the forming surface. The paper stock is usually supplied under a hydraulic head suificient to cause a desired flow of stock to the fomiing surface and it has been common practice to obtain this head by employing an open top rectangular box, commonly called a IRAQ- box, in which a level of stock is maintained a is sufiicient height above the to surface a give the desired head.

As pointed out in my original application, a paper stock is frequently tum- .of various components including water which has ed through the forming surface (commonly d white water), recirculated stock, and fresh incoming stock. It has heretofore been a c a, 1-; a practice to mix the various components or the paper stock in the headbox. e practice each of the components is introduced into the headbox through a separate pipe and it has been assumed that the natural turbulence resulting from such a procedure would produce adequate mixing. However, this is y not accomplished under present day operati ditions. Pockets of diflerent consistency stcc tend to form in the corners of the headland and this-segregation causes streaks of uneven consistencies of stock to pass to the forming sur turbulence of the mixing operationtends to increase the air content of the stock.

In accordance with the disclosure or my crisinal application, the of the rious com= ponents of stock is accomplished at a int suificiently remote from the to surface to per= ment of a smooth and uniform flow of stock before the stock reaches the forming surface. The

mixing step and the airremoval step are physlcally separated from one another. The mixing is accomplished before the stock reaches .the'

headbox and hence does not interfere with the desired functions of the headbox which are the maintenance of a constant flow level and the elimination of air or other gaseous material from thestock. An improved typeof headbox and mixing device or flowmixer is disclosed, the

I claims of the present divisional application directed to the improved headbox construction.

Figure 2 is a cross-section of the vat and flow 25 spreader taken along line 2-2 of Figure 1; and

Figure 3 its view of the vat end showing the white watercompartment in section taken alon line t-t oi Figure l.

Referring to the drawings, and more particularly to Figure 1, there is shown a vat oi generally rectangular shape indicated at i and containing a foraminous' cylinder mold 2 rotatably supported by the bearings a, only one of which is shown. The mechanism for rotating the cylinder mold forms no part of the present invention and hence is not shown. Stoclzis supplied to the vet 8 through a flow spreader d, which is of such shape and cross-sectional area as to spread the flow of stock to the full machine width with substantially noschange or with a slight increase in 3 stock velocity. Upon entering the vat i, the stock passes througha conduit 5 (see Figure 2) to the outer vat circle space a which is formed by an outer vat circle l of generally cylindrical contour, and an inner vat circle 8 of similarcontour, the vat circle i being rigidly sebured to the vat ends and the vat circle d adjustably secured to the vat ends in a manner more fully ducribed hereinafter. The vat circles l and 8 are constructed of sheet. metal, preferably of copper, in order that the desired degree of flexibility may be obtained. A washout connection to is provided near the bottom of the vat circle l and a similar washout connection 9b is provided near the bottom of the vat circle 8 to facilitate cleaning of the vat circle spaces when it is necessary to change the type of stock supplied to the machine in order to produce a, different type of paper board. From the vat circle space 6, the stock flows over the smoothly curved upper end ll] of vat circle 8 into the inner vat'circle The curved surface It] is analogous to the making boards of the vats known to the prior,art and-maybe so described. g

As the stock passes through the inner vat circle space H, the cylinder mold 2 rotates in a counterclockwise direction, as shown, and a portion of the water from the stock passes through the foraminous surface of the cylinder mold forming (not shown), where it is used as a diluent, and a second portion flowing to a mixing device 36. In the mixing device 35 the white water is thoroughly mixed with the recirculated stock coming from the lines |3 and I4. As pointed out in my.

original application it has been found that the most thorough and intimate mixture is obtained by joining the two streams of flow in such a manner that their cross-sectional areas are small and their velocities high at the point of mixing, and hence the diameters of both pipes are reduced at the point of joining. The recirculated stock a web of fibers on the surface of the mold, which J is removed near the topof the mold after it.has

emerged from the stock. The water passing The'inner vat circle 8 is fabricated in such a manner as to be supported by three adjusting bars l8, l9, and 20, preferably of tubular cross-section.

These adjusting bars are covered on both sides by the sheet metal forming the inner vat circle so that both of the-vat circle spaces are completely streamlined and no obstruction is pre-- sented to the flow of stock. The adjusting bars are in turn supported by a series of movable plates 2|, 22, and 23 located at the vat ends (best 1 shown in Figure 3). Adjustment of the clearance between the vat circle 8 and the periphery of the cylinder mold is accomplished by loosening the bolts 24 which hold the movable plates in position and moving the plates in the desired direction. Normally the adjustable bar |B will be positioned further from the periphery of the cylinder mold 2 than will the bar 20, and the bar l9 will be positioned'at an intermediate distance from the cylinder mold in order to form a vat circle space having a decreasing cross-sectional area which will partially compensate for decreases in the quantity of stock due to water flowing through the surface of the mold.

The water which flows through the surface of the cylinder mold'is removed at the end of the mold and flows into two white water compart ments 25 and 26 at the vat ends, the compartments being separated from the vat ends by the spacer rings 21a and 21b. Suitable seals should be provided at the ends of the cylinder mold 2 to prevent stock in the vat circle space H from flowing into the interior of the cylinder mold. Such-seals are well known in the art' and hence are not shown in detail. As shown in Figure 3,

the white water compartments contain an adjustable dam having a rack 29 rigidly attached thereto. Raising and lowering of the dam is accomplished by rotation of the pinion 30, which in turn is actuated by rotation of a knob 3| located on the outside of the white water compartment. The portion of the white water which overflows the dam 28 is the excess white water and flows out of the white water compartment through a line 32 which leads to a suitable point of disposal. The remainder of the white water, constituting the major portion thereof, is pumped by means of the white water pump from the white is introduced at the most restricted portion of the mixer and hence at the point where the white water velocity is a maximum, thus insuring adequate mixing of the two components. From the mixer 38 stock passes through pump 31 to a second mixing device 38 of similar design where fresh incoming stock from the screens (not shown) is introduced through the line 39.

Stock from themixing device 38 passes to a conical upfiow headbox 40 comprising an outer inverted cone 4| and an inner inverted cone 42 concentric therewith and forming an annular space 43. The outer cone 4| is provided at its topwith a short cylindrical section 44. If desired, the inner cone 42 may also be provided with a cylindrical section which may be made adjustable in height. It is desirable that the dimensions of the cones 4| and 42 be such that at the top of the inner cone the annular area between the two cones approximately equals the cross-sectional area, of the inner cone. Stock flows upwardly through the inner cone 42 at a constantly decreasing velocity,. passes over the dam formed by the upper edge of the cone 42 and flows downwardly through the annular space 43 at a constantly increasing rate. Because of the upward direction of flow of the incoming stock and the relatively low stock velocity at the dam 45, headbox 40 is well adapted to remove air andother gaseous materials from the stock and improve the smoothness of flow. Furthermore, variations in the rate of flow of stock will cause only relatively small turbulence or changes in the liquid level in the headbox because of the large overflow area of the dam 45 and the large area of the free liquid surface. It is to be noted that this type of headbox has no dead corners where stock segregation can occur and is much easier to"wash up than the usual type of headbox.

From the annular space 43 stock flows through an underfeed supply pipe 46 which is preferably of a relatively large size and thence to the flow spreader 4 and the vat The machine of the present invention makes possible the productionof a paper board h'aving a; substantially greater uniformity than was heretofore possible. The double circle vat enables the machine operator to control the stock velocity ratio in such a manner as to obtain the formation of characteristics desired, uniform fiber 'deposition around the vat circle, and further provides a full pass in the machine direction to iron out minor irregularities in the flow of stock before the stock reaches the forming surface of the cylinder. mold, The relative machine and cross tear and tensile tests, for example, can be varied at will between wide limits andthe optimum stock velocity can be obtained at every point around the vat circle. Positive, rapid, and complete mixwater compartment through the line 33, whence ing of the various components of the stock is in- .sured. by the improved mixing devices, and this mixing takes place at a point remote from the rennin; surface. The upflow headbox insures proper elimination of air from the stock and the new spreader spreads the flow to the full width of the machine with no sudden changes in stock velocity to produce unnecessary turbulence at this critical point in the process. Thus when the stock iinally reaches the iorming surface, eddy currents have been substantially eliminated and the how of stock approaches theoretical streamline flow much more closely than has heretoiore been possible.

Since many embodiments might be made of the above invention, and since many changes misht be made in the embodiment above disclosed, it is to be understood that all matter hereinbei'ore set forth is to be interpreted as illustrative only and not in a limiting sense.

I claim:

In a paper machine of the type wh'erein a sheet is formed by bringing a paper stock comprising a pulp suspension into contact with a forming uriace. a headbox comprising: a vertically arranged outer conduit having a cross-sectional area that increases gradually and continuously from the bottom of said outer conduit to the top of said outer conduit; an inner conduit vertically arranged within said outer conduit and having a cross-sectional area that increases gradually from the bottom of said inner conduit to the top of said inner conduit; said inner and outer conduits being ccaxially arranged; the upper edze or said inner conduit serving as an overflow means between said conduits; means for simplyina stock to the inner of'said conduits at a point near the bottom or said inner conduit; and means tor withdrawing stock from the outer of said conduits at a point near the bottom of said outer conduit.-

whereby stock flows upwardly throush the inner conduit at a gradually decreasing velocity, over said overflow means into the outer conduit and all oi. the stock passinc over said overflow means 20 flows downwardly through-said outer conduit at a

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