US3009517A - Pressure headbox construction - Google Patents

Description

NOV- 21, 1961 D. R. WEBSTER PRESSURE HEADBOX CONSTRUCTION 2 Sheets-Sheet 1 Filed June 18, 1958 Nov. 21, 1961 D. R. WEBSTER PRESSURE HEADBOX CONSTRUCTION 2 Sheets-Sheet 2 Filed June 18, 1958 United States Patent O f" 3,009,517 PRESSURE HEADBOX CNSTRUCTION David R. Webster, Mount Royal, Quebec, Canada (1070 Graham Blvd., Apt. 1, Montreal 16, Quebec, Canada) Filed .lune 18,1958, Ser. No. 742,894 6 Claims. (Cl. 162-339) The present invention relates to paper-making and more particularly to an adjustable headbox for a paper machine. This is a continuation-impart of co-pending US. application Serial No. 378,323, iitled September 3, 1953 now abandoned.

Any paper machine headbox is intended to transform circular pipe flow to a broad thin ribbon-like jet of regulated speed and thickness. 'Pwo chronic problems inherent in headboxes of prior art are (l) that this transformation is subject to uneven dispersion and turbulence, 'and (2) that the headbox frame tends to bulge under liquid pressure and hence the outlet oriiice (known as a slice) distorts accordingly. Both defects cause an uneven sheet of paper.

Attempts have been made to overcome the first problem of uneven dispersion and turbulence by the use of large dispersion chambers, multi-pass bafiies, holey rolls, guide vanes or rectiiier plates, and other well-known means. These all have the common disadvantage of being costly, awkward to maneuver, conducive to slime growth, and by their construction tend to obstruct access for cleaning the head-box.

As an example, one known device, shown in U.S. Patent No. 1,889,819 to Berry, issued Dec. 6, 1932, distributes liquid `across the width of the paper machine by means of a conduit that is stationary, horizontal, and at right angles to the paper machine direction, and is provided with a horizontal slot in its upper part. Discharge from this slot is dispersed by a holey roll also positioned horizontally and at right angles to the paper machine direction and surrounding the inlet conduit. This arrangement may be proportioned for any desired head, and its inlet conduit may be ilooded over, but the upper portion of the holey roll is maintained above the liquid level for clean-ing purposes.

The use of a holey roll in the Berry disclosure or other similar kprior art constructions is to disperse the undesired eddies and cross currents in a minimum of space. While such an arrangement does parti-ally overcome the problems mentioned above, it still has advantages inherent to the use of a holey roll, for example:

, (a) It obstructs the headbox for cleaning and maintematico;

(b) Its necessary end seals are apt to leak either outwardly or, if lubricated by a water jacket, inwardly to cause water streaks .in the stock stream;

(c) It requires driving'power, which incr-eases if the seals are tightened `to become nearly watertight;`

(d) As a moving part it needs inspection. and maintenance;

(e) At high flow velocities it 4can .produce undesirable turbulence patterns;

. yIt harbors inaccessible slime growth;

(g) A lholey rolll which protrudes through vthe liquid surface, if equipped with any cleaning device, will need .some means to .clean also the surfaces of the lcleaning device orfslime and'lumpsvwill 'accumulate there from the drip, vapor, and splash faster than slime would grow on Ja submerged roll becauseof bacteriathat thrive in moist air. Y

(h) Knowncleaning devices are arranged to scrape'or .spray the inner and outer cylindricalsurfaces of :the holey corners which are subject to 3,009,517y Patented Nov. 21, 19,61

mentioned above there also is no means to keep the surfaces of the cleaning device free of slime.

The present invention aims to provide a pressure headbox which wh-ile omitting a holey roll continues to perform its function by impinging all iiow in a direction away from the slice in a ribbondike stream against target plates so arranged as to create a swirl chamber where eddies and cross currents are dissipated before the ow proceeds to a nozzle chamber. Swirl chambers in general are known in prior art such as disclosed in U.S. Patent 2,329,799, issued Sept. 21, 1943, to Thorsen, and Canadian Patent 464,219, lissued April 4, 1950, to Hurt/er', but these are not constricted in accordance with the present invention as evident below where the swirl feature is particularly described as part of the dispersion chamber.

The present invention also aids dispersion by splitting the flow into two identical streams the width of the paper machine, each stream thereby representing half the thick.- ness of paper to be made. Splitting the ilow in to -two streams is known in prior art, as disclosed in U.S, Patent 1,534,080, issued April 21, 1925, to Russell, but is not in accordance with the present invention as evident below where the twineiiow feature is particularly described as part of the dispersion chamber.

Attempts have 'been made to overcome the second problem previously mentioned of slice distortion Aby providing tie rods extending through the stock stream, or by providing large beams spanning the paper machine width to permit a clear headbox interior, or by the use of long nozzles that convert static pressure to kinetic energy thereby relieving thrust against the slice walls. These prior art arrangements again have certain disadvantages, for example, tie rods tend to accumulate lumps of slime or cause streaks in the stock flow. An example of the tierod type of construction is shown in U.S. Patent 1,909,150, issued May 16, 1933, to Bell-Irving et al. Headbox struc? tures embodying large beams spanning the paper machine Width are costly, and no matter how large the beams may be, they intrinsically must have a maximum deection lat mid-span of the paper machine. Examples of this large beam type of construction are shown in U.S. Patents 1,909,150, May 16, 1933, to Bell-Irving et al. and 2,268,- 840, I an. 6, 1942, to McGuire et al.; and Canadian Patent 464,219, April 4, 195,0, to Hurter mentioned above. The form of headbox utilizing elongated nozzle structures in general occupy much space by reason of their structure. An example of this type o f construction is shown in U.S. Patent 2,677,991, issued Mgay 11, 1954, to Goumenioul.

The construction of the present pressure headbox is such that it avoids the problems introduced by -prior rart l line'is nozzle-shaped, w-ithout beams andV levelling ,screws projecting exten'orly as in prior art, so that the fheadbox can -feed into a confined space such as into 'a v.nipbetween two rolls.

More specifically, the headbox construction ofthe :in--

vention includes in combination, a horizontal inietzconduit at vright angles to the paper machine direction, im- .perforate throughout its 'length except Afor petforat'e inlet means such as a slot directed 180 away `from''an-.oriiice to` atmosphere at the breast roll; and asurrounding Acasing against the rear of which liquid from :the ,inlet conduit roll, vbut do not effectively clean the perforations. A s' slot impinges to spread out and then to detlect along ithe, i! l casing walls to be converged between the inlet conduit exterior and the casing Walls, which are disposed relative to each other to provide two (2) apertures the width of the paper machine, and prior to which liquid is mixed and dispersed by its initial impingement; and a nozzleshaped slice diametrically opposite the inlet slot provided with means to regulate the slice orifice to atmosphere. The casing walls at the impingement zone, twin venturi passages, and nozzle chamber are conjoint and in watertight connection with a pair of vertical walls at either side of the paper machine admitting the inlet conduit. A frame is provided which includes structural features whereby headbox bulging is limited to a pattern of small similar bulges instead of a large bulge culminating to a maximum at mid-span of the paper machine width, as occurs with known clear-passage headboxes. This frame 1n turn is provided with support means capable of three (3) movements, up-down, forward-backward, and rotation through a full circle which is not possible in known headbox constructions.

Having thus generally described the nature of the invention, particular reference will be made to preferred embodiment as illustrated in the accompanying drawings, and in which:

FIGURE 1 is a plan view of an adjustable pressure headbox in accordance with the invention.

FIGURE 2 is a view in rear elevation of FIGURE l.

FIGURE 3 is a view of one end of the construction of FIGURE 1 with the slice orifice shown in operative position relative to the breast roll of a Fourdrinier wire.

FIGURE 4 is an enlarged sectional view of FIGURE 1 along the line 4--4 to illustrate the internal construction more clearly.

FIGURE 5 is an enlarged detail view in plan of a portion of the headbox structure proper to illustrate the outlet or slice lip control construction more clearly.

With particular reference to FIGURE 4 of the drawings, the main elements of the present construction include a horizontal inlet conduit, a dispersion chamber, a slice, a frame, and with particular reference to FIG- URE 3, a support. Each is described in detail under separate headings below, In FIGURES 3 and 4 a portion of a paper-machine wire A and a breast roll B are shown with reference to a preferred positioning of the pressureheadbox construction.

Inlet conduit A horizontal inlet conduit is disposed at right angles to the paper-machine direction and is provided with a slot or line of holes 12 `along the length of the conduit and is adapted to discharge liquid from the conduit 10 as a ribbon-like jet wholly in a direction diametrically away from the slice and breast roll.

Dispersion chamber A casing 14 envelops the inlet conduit 10 in spacedapart relationship so that discharge from the inlet slot 12 all impinges in a direction 180 away from the slice against the rear wall 16 of the casing, as against a target plate, and there flow splits evenly into two ribbon-like streams and spreads to impinge a second time against the top wall 18 and bottom wall 20 of the casing where it is diverted in a direction opposite to its original discharge from the inlet slot. By having reversed, the ow forms a perimeter around a more quiescent body of liquid in which the encircling flow by rubbing contact in opposite directions induces a swirl. The swirl causes an abundance of shearing within the liquid so that cross currents and any large turbulences are dissipated without the need for a holey roll. This impingement and swirl zone comprises the dispersion chamber 21. `Flow along the casing walls may further be dispersed if desired without enlarging the headbox, by roughening the casing walls, such as by providing corrugations having ridges parallel to the inlet conduit.

Flow then proceeds through two narrow similar passages 22 the full Width of the paper machine, which passages 22 are formed between the outer periphery of the inlet conduit 10 and the casing top and bottom walls 18, 20. These twin passages 22 by being relatively narrow cause a pressure change so that cross currents and eddies are confined within the dispersion chamber 21. As the headbox is of the full-flowing type, liquid under pressure fills the dispersion chamber 21. Each of the twin passages 22 has a `convergent approach and a divergent exit formed by the periphery of the inlet 10 and adjacent wall of casing 14 to create a Venturi effect on the flow pattern. This Venturi effect creates hydraulic shear planes and thereby mixing that prevents stock fibers from collecting into bundles. All flow passes through these unobstructed Venturi passages 22 instead of through the multi. plicity of orifices found in a holey roll as is common in the prior art.

Thus the dispersion chamber 21 intensifies the dispersion process over known art and performs the function of the holey roll by impingement, by swirl, by corrugations if desired, and by venturi effect. After the twin passages 22 the flow expands into a nozzle chamber 25 formed by the converging portions 25a, 25b of the walls 13, 20 to merge into a single stream, and then the ow contracts as it accelerates toward the opposed slice lips 30a, 30h disposed at the terminal ends of the portions 25a, 25b. The whole dispersion process provides flow symmetrical about the plane of the jet to atmosphere, and this balance of flow averts turbulence in a novel manner.

The preferred symmetrical construction is chosen because of the following merits:

(l) Symmetry splits the stream so that possible eddies can influence not more than half the flow thickness. Where there are two (2) streams this ensures optimum control over the dispersion of eddies.

(2) Symmetry provides the straightest possible path for both streams after the dispersion chamber and thereby a minimum shearing disturbance Within the liquid.

(3) Symmetry provides a balanced impulse as the two streams merge, and thereby a minimum interference at their confluence.

(4) Symmetry ensures that the two streams will have similar velocities because they have been subjected to the same feed, the same cross section, and the same wall friction.

(5) Any nozzle tends to stabilize flow, but symmetry provides two similar flows feeding the nozzle and thereby further aids flow stability.

For the above reasons a symmetrical headbox is more efiicient at stabilizing iiow than an unsymmetrical one.

Hence, the first chronic problem mentioned above of uneven distribution and turbulence is overcome in this invention by a combination of an inlet conduit and a dispersion chamber to transform a circular pipe flow to a broad stable stream the width of the paper machine. The slice then regulates this stream. The headbox end walls 40a, 4612 at each end of the casing 14 are separate flat walls secured, for example, by bolting to end flanges provided on the top, bottom and end walls with a free portion adjacent the lips 30a, 30b.

The slice part includes essentially three (3) elements: (1) a nozzle 25 for stabilizing flow, (2) a pair of bars 39a, 39b for producing micro turbulence, and (3) a cantilever means 52, 152 for adjusting the slice lips 30a, 30b.

The nozzle portion 25 performs the well-known function of accelerating the stock smoothly and without shock toward the slice lips 30a, 30b. As is also well known, when stock accelerates in this manner shear planes develop within the liquid in the plane of the jet to atmosphere. The fibers thereby become aligned in the direction of flow, which alignment strengthens the paper tensile capacity in the machine direction, but weakens it in the cross-machine direction. This suits only certain grades of paper.

The bars 39a, 39h are provided to construct the flow passage with a venturi shape and thereby to create micro turbulence. They are placed removably near the slice lips 30a, 30b, where by localized turbulence they re-orient the fibers and thereby impart cross strength to the paper. The cross-section of the replaceable throat bars 39a, 39b may be selected to suit the nozzle proportions, the machine speed, and the grade of paper being produced.

Adjustment to the slice lips 30a, 30b is accomplished in the following manner. Levelling means are provided that are adapted to angularly deect cantilevers 52 attached to each slice lip 30a, 30b by brackets 31, instead of the usual arrangement disposed to impart direct thrust to the lips by rods customarily perpendicular to the slice ow direction. The cantilevers 52 are spaced, as is customary with rods in prior art, and adjustment is effected while the paper machine is in operation.

The top lip 30a is arranged for overall adjustment through an eccentric shaft 54 to which all its `contilevers 52 are attached. Each cantilever 52 may also be adjusted individually at its attachment to the eccentric shaft 54. Adjustment is imparted through threaded eye-bolt 56 providing a link between eccentric 54 and cantilever 52 with its eye 57 fitted around the eccentric shaft 54 and its threaded bolt 58 aligned nearly perpendicular to the cantilever 52. A knurled nut 59 is utilized to secure the threaded bolt 58 in sliding contact with the end of the cantilever 52. By turning the knurled nut 59, one cantilever 52 is given angular adjustment, whereby the slice lip 30a is deected only locally. By turning the eccentric 54 all cantilevers 52 deflect. The eccentric shaft 54 is fitted to the headbox frame, indicated generally at 60, outside the casing 14 and adjacent to the dispersion chamber 21 so that the cantilevers 52 lie almost parallel to the nozzle walls 25a, 25b.

The slice bottom lip 30b is arranged only for overall adjustment through a similar eccentric shaft 62 to which the ends of the cantilevers 152 are attached directly. Each eye 157 around this second eccentric shaft 62 is elongated from the normal circular cross-section to accommodate the displacement of the eccentric shaft 62 in the axial direction of the cantilever. By rotating the eccentric shaft 62 through a selected arc, a measured deectionis imparted to the whole bottom lip 30b, and the jet thickness thereby is regulated.

Frame The frame 60 encases the top, rear, and bottom of the head-box to support the casing 14 against bulging from liquid pressure, which is 'the same function as performed by the frame of any pressure headbox. In opposition to the usual construction the main containing beams 61 of the present frame are inthe machine direction instead of in the customary direction spanning the paper machine width. A headbox poses special problems in that no support can be allowed to penetrate the broad thin stream the width of the paper machine. Structurally therefore, a headbox must be considered as needing one open side. Heretofore headboxes either had also an open top which prevented placing any beams in the machine direction across the top of the headbox, or headboxes of the closed pressure type have been so massive that beams in the machine direction, while so placed as secondary supports, have had too long a span to be capable of imparting enough rigidity to maintain jet thickness.A The compactness of the present headbox and thus its short span in the machine direction makes it feasible now to place the main beams in the machine direction. l

Each main beam 61 of the present headbox frame is arranged in an almost U-shaped path, seen most clearly in FIGURE 4, so that the slice discharges through the open end of the U. The ends of the U converge slightly to conform to the profile of the nozzle chamber 25. Thus each arm 61a, 61b of the U is in effect a cantilever continuously loaded, and its cross-section can diminish toward the outlet, because the residual area of load diminishes toward the outlet. Each beam 61 acts somewhat as a common C clamp with the result that the live load of liquid pressure is restrained locally at each beam 61', y

leaving only the dead load of liquid and structural Weight to be transmitted toward the headbox end walls 40u, 4017. These end walls of course restrain the liquid pressure of their immediate locality.

In addition to this cantilever loading effect, the nozzle 25 converts static pressure to kinetic energy whereby the unit pressure thrusting against the nozzle walls 25a, 25h also diminishes toward the outlet. Thus the main beams or U ri-bs 61 can 4again taper in cross-section which permits a lighter frame than in known headbox constructions.

The present construction providing a lighter frame at the nozzle relieves the whole headbox of a certain dead load, and thereby permits lightening other parts of the supporting frame 60. Also, the headbox volume is so small compared to known headboxes that the weight of liquid is relatively small, permitting a further weight reduction of the frame.

The U ri'bs 61 are joined by X bracing 65 along the casing rear wall 16 opposite the slice-opening to stiften the headbox against twisting. The top Wall 18 and bottom wall 20 with their portions 25a, 25b of the casing 14 act as beam flanges and the rear wall of the casing acts as a beam web to help support the headbox across theA span of the paper machine width. By these U shaped frames the second chronic problem of prior art, previously mentioned, of the frame bulging to a maximum at mid-span is overcome through limiting the bulging to a pattern of small similar bulges. Further, the tapering frame outline permits using this headbox close to a confined space such as close to the nip between two rolls.

Support a full circle and permits a Asingle adjustable support at either side of the paper machine.

A prefeired form of this support yis shown most clearly in FiGURES l, 2 and 3 and as previously described the entire headbox is supported on the inlet conduit 10V which in turn is supported for rotation on a supporting frame embodying means whereby vertical and horizontal adjustment can bemade through hand wheels. The supporting frame inpturn is secured to the paper machine frame in the position desired.

T he rotation of the headbox is accomplished through the following arrangement.

beyondthe casing 14 at each side to serve as axles for worm gears 132. The ends of the conduit 10 extending beyond the gears 132 are journalled in suitable bearings ,j

provided in spaced apart supporting frames 1'70.A The gears 132 are in meshed engagement with worms 134 mounted on shafts-172 also journalled, in a vertical position, on the opposed supporting frames 170. The shafts 172 extend beneath each worm 134 to a connection and bevel gears 176 are mounted on the lower ends of the shafts 172. The bevel gears `176 are in meshed engagement with corresponding bevelled gearsY 178 mounted on each end of a shaft 180 which extends between the frames 17u across the width of the supportingv arrangement. Crank arms 182 are provided on each end of the shaft 180 so that it can be rotated from either side of the ma- 5 A." chine. Rotation of the shaft 181), is transmitted through the'gears 176, 178, the shafts 172, Worms 134 yand the worm gears 132 to the conduit 10 so that the pressure headbox can be rotated about a 360 `arc relative to the frames 170.

As is shown most clearly in FIGURES 1 and 2 portions of the conduit 10 extendv As a further means of adjustment the frame supporting members 170 are each mounted for vertical sliding movement in supporting standards 184. As shown in FIGURE l, each member 170 is provided with a wedge tongue 186 along the rear edge which slidably fits in a corresponding groove 188 provided in the standard 184. Each member 170 is supported relative to the respective standard 184 by the threaded engagement of a threaded shaft 190 journalled for rotation on a lower extension 185 of each standard 184. A worm gear 192 is secured to the bottom portion of each of the threaded shafts 190 and is disposed in meshed engagement with a worm 196 mounted on a shaft 198 extending across the supporting arrangement. The shaft 198 is adapted to be rotated through a crank-arm 200. With this arrangement, rotation of the worm 196 rotates the worm gear 192 and shaft 190 and causes a corresponding vertical movement of the members 170 relative to the standards 184.

The spaced standards 184 in turn are mounted for horizontal sliding movement in spaced apart base portions 202. The bases 202 are provided with guideways 204 into which the bottom portions of the base ofthe standards 184 slidably tit. The standards 184 are engaged by threaded shafts 206 on each of which there is mounted a bevelled gear 208 in meshed engagement with corresponding bevel gears 210 supported on a shaft 212 extending across the device. Rotation of the shaft 212 by crank-arms 214 causes a corresponding rotation of the threaded shaft 206 and a consequently horizontal movement of the standards 184 relative to the base portions 202.

l claim:

l. A pressure headbox of the full-flowing type adapted to deliver stock to a paper machine comprising in combination, a distributor conduit with perforate inlet means disposed diametrically opposite an unobstructed orifice formed by a pair of slice lips, said inlet means extending substantially the axial length of and subtending a minor segment of said conduit, all the remaining major segment of said conduit being imperforate, a casing symmetrically disposed in spaced-apart relationship around each of said minor and major segments, said casing forming an impingement wall adjacent said minor perforate segment and forming with said conduit an unobstructed Venturi passage ilanking symmetrically either side of the exterior surface of said conduit, and forming a wedgeshaped chamber adjacent and extending outwardly from said major imperforate segment, said casing at the apex of the wedge-shaped chamber terminating in opposed slice lips forming therebetween said unobstructed orice disposed diametrically opposite said perforate inlet means, said impingement-wall, Venturi-passage, and wedge-chamber parts of the casing being conjoint and in watertight connection with a pair of vertical walls at either side of said paper machine admitting said distributor conduit, means for adjusting said lips, and means for adjusting said headbox relative to said paper machine.

2. A pressure headbox as claimed in claim l, wherein said means for adjusting said slice lips includes a series of levelling rods rigidly attached at intervals along said slice lips, said rods lying almost parallel to the wedge- 8 shaped portion of said casing, and control means to defleet said rods through a small arc.

3. A pressure headbox as claimed in claim l, wherein bars having a cross section adapted to suit the tlow conditions are attached inside the headbox casing in the cross machine direction and near the slice lips thereby forming a stil and alterable means for producing localized turbulence in a liquid jet from said headbox.

4. A pressure headbox as claimed in claim 1, wherein said means for adjusting said headbox relative to said paper machine includes a series of main framing beams, each of said beams lying in a vertical plane in the machine direction and forming a continuous path around three sides of the headbox casing forming said impingement, Venturi, and wedge-shaped chamber walls, each of said framing beams being tapered from a minimum at both ends to a maximum at the half length which occurs adjacent said perforate inlet means, whereby the apex of said wedge-shaped casing including said unobstructed slice is adapted to enter a confined wedge-shaped space in a paper machine.

5. A pressure headbox as claimed in claim l, wherein said means for adjusting said headbox relative to said paper machine comprises full-circle rotation means located at said distributor conduit entry ends.

6. A pressure headbox of the full-owing type adapted to deliver stock to a paper machine comprising in combination an inlet conduit with perforate inlet means disposed diametrically opposite an unobstructed orifice formed by a pair of slice lips, said inlet means extending substantially the axial length of and subtending a minor segment of said conduit, the remaining major segment of said conduit being imperforate; a dispersion chamber disposed adjacent said inlet conduit diametrically opposite said slice lips and symmetrically about each of said minor and major segments, said chamber anking symmetrically in close proximity either side of said conduit forming therebetween twin Venturi passages, said chamber adapted to receive flow as an impingement from said conduit in a direction diagonally away from said slice lips creating a symmetrically split reversal of ow toward said slice lips thru said twin Venturi pasages; a slice in the shape of a wedge-like nozzle conjoint with said dispersion chamber, said slice symmetrically disposed about said minor and major-segments and having an unobstructed adjustable orifice to atmosphere at the apex of said wedge shape; said dispersion chamber and slice having a watertight vertical wall in common at either side of said paper machine, each such wall including an inlet opening for said inlet conduit.

References Cited in the le of this patent UNITED STATES PATENTS

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