Multiple ply web former with divided slice chamber

Abstract

A machine for making multi-ply webs such as paper and having a traveling foraminous forming surface with a headbox having a tapered slice chamber and a slice opening delivering a stream of stock to the forming surface with the headbox and slice chamber being partitioned with the partitions being continuous across the width of the headbox and extending fully to the slice opening with the partitions in the slice chamber being trailing self-positionable flexible elements extending fully to the slice opening and each partition having additional trailing self-positionable flexible elements with the headbox and slice chamber being divided into three chambers in one form and long fibered stocks delivered to the outer chamber with a high ash content stock delivered to the intermediate chamber to permit dewatering of the intermediate layer without excessive loss of ash.

Parent Case Text

The present application is a continuation-in-part of my copending application, U.S. Ser. No. 204,545, filed Dec. 3, 1971, entitled "Multiple Ply Web Former", now abandoned.

Description

BACKGROUND OF THE INVENTION

The present invention relates to improvements in machines and methods for making multi-ply webs from plural supplies of stock, each having fibers suspended in a liquid. More particularly, the invention relates to an improved high speed forming arrangement which is particularly well adapted to making a multi-ply paper web.

In the formation of multi-ply webs, as with single ply webs, increases in machine speeds and increases in requirements of stock specifications, have created operating problems in that continued and improved high quality paper webs have been demanded which are manufactured at higher speeds than heretofore. In making multi-ply webs, it has been conventional to lay down and form successive layers or plies on a forming surface and to join the plies after they are wholly or partially dewatered. For example, in U.S. Pat. No. 3,598,696, Beck, layers of stock are successively laid onto the same forming surface with each layer being partially dewatered prior to laying successive layers thereon. With this type of mechanism and other mechanisms where the individual layers are more fully dewatered before laying successive layers thereon, a first layer of stock is placed on the forming surface and subsequently a second layer of stock placed over the first. Because the outer or lower layer is partially or fully drained before the successive layers are placed thereon, the water from the successive layer must pass through fibers which are already oriented in a mat with respect to each other creating a bar to the fresh water coming down from the top layer. Also, a disturbance of the lower layer can occur because of the water rushing down through the fibers from the top layer.

Other arrangements to form multi-ply paper are shown in patents such as U.S. Pat. No. 3,471,367, Chupka, wherein twin opposed wires are used, and one layer is formed, being dewatered through both wires and thereafter a subsequent layer of stock is placed on the preformed first layer. This type of construction encounters certain of the problems above discussed, and because one layer is preformed, the second layer dewaters unequally through the first layer or through the other opposed wire. Further, this type of arrangement creates problems in that it does not achieve as good an interlace or adhesion between the two separate layers as is desired.

Other arrangements for forming multiple layered webs are those such as shown in U.S. Pat. No. 3,255,074, Salomon et al wherein separate stocks are supplied, but the stocks are permitted to intermingle prior to being released from the slice opening onto the forming surface. The intermingling of stocks prior to emitting from the slice does not maintain a fine scale turbulence in all sectors of the flowing streams of stock and does not form a web of as well defined layers as desired in certain circumstances. Also, with certain arrangements of the prior art where multiple layered webs are formed using different types of stocks such as those having reclaimed fibers for an intermediate layer and virgin fibers for an outer layer, an intermixing of the white water removed from the layers is undesirable, but necessary with prior art structures.

It is an object of the present invention to provide an improved headbox structure wherein an improved multi-ply web can be formed having better properties than webs heretofore available such as having better defined layers and having layers which are fully interlocked, that is, which are substantially homogeneous in fiber interlocking, but yet distinct and separate from the fibers layers. With this type of arrangement and with this objective being met, thinner outer layers of long fibered or virgin stock can be used reducing the cost of the paper being made.

A further object of the invention is to provide an improved headbox structure for making multi-layered paper wherein a fine scale turbulence is maintained in each of the stocks completely up to the time of discharge from the slice chamber opening without an intermixing of the stocks so that a better formation of each of the layers of the web is attained, yet with full interlocking adherence between the layers. A feature of the invention is that the headbox constructions permits use with either a single traveling forming wire wherein the multi-layers are discharged simultaneously onto the top of the wire, or can be used with plural looped traveling forming wires wherein the stock is delivered from the headbox slice opening into the throat formed between the wires.

A further object of the invention is to provide an improved headbox arrangement wherein a multi-ply paper web can be formed having an intermediate layer of higher ash content than heretofore available.

Another object of the invention is to provide an improved and unique structure for delivering a plurality of different stocks of different physical characteristics to a forming surface and at the same time maintaining them in their multi-ply layer arrangement and maintaing full fine scale turbulence within each of the stocks to prevent flocculation and without having this turbulence cause intermixture of the stock for the plies on the wire, but causing interlacing of the fibers between plies.

A still further object of the invention is to provide a unique and improved mechanism wherein a multi-ply paper web may be formed and multi-layers of stock delivered to a twin wire forming unit where each of the layers are dewatered through their own wire at a dewatering rate optimumly suited to the stock and ply.

It will be recognized by those versed in the art that various forms of the invention can be employed within the spirit and scope of the principles of the invention, and that various embodiments which are intended to be covered herein may be used as will be appreciated from the teachings of the principles of the invention in connection with the disclosure of the preferred embodiments in the claims, specification and drawings, in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat schematic side elevational view of the forming section of a paper machine delivering stock to twin forming wires constructed and operating in accordance with the principles of the present invention;

FIG. 2 is a schematic side elevational view of a headbox constructed in accordance with the principles of the present invention and arranged to form a web having an intermediate layer of a high ash content;

FIG. 3 is a fragmentary enlarged sectional view taken through a paper web illustrating the constituents of the web; and

FIG. 4 is a somewhat schematic side elevational view of another form of headbox in accordance with the invention.

DESCRIPTION

Looped traveling forming wires 10 and 11 are positioned so that they are guided together in a forming throat 12. Following the tapered forming throat they converge to provide a web forming run along which a multi-ply web is dewatered through the wires. The wires are foraminous wire screens of the type used in the formation dewatering of paper webs and may be of the same porosity and of the same structure. However, in accordance with the principles of the present invention where a two-ply web is formed between the wires, each web is dewatered optimumly in accordance with the characteristics of the fibers which make up the web and, therefore, in some instances the opposing forming wires may have different physical characteristics consistent with the nature of the stock of the layer against the particular wire.

For convenience of description, the web will be described as being a two-ply web with a brown layer formed against the wire 10 and a white layer formed against the wire 11. Multi-ply webs of different constituents may be formed as is well-known to those skilled in the art, and the brown and white multi-ply web is frequently employed in environments wherein a brown more coarse and less expensive layer must be provided for bulk and strength and a thinner better appearing white layer provided on the other side of the web which will receive printing and be better suited for exposure to the outside of a container formed from the web.

The wires 10 and 11 are guided into the forming throat over suitable guide members shown in the preferred arrangement in the form of rolls 14 and 15 respectively. These rolls may be on shafts which are adjustable to control the position of the rolls and the width of the entry throat 12. Suitable doctor blade scrapers 14a and 15a are provided for the rolls 14 and 15. Various structural framework pieces are shown in the drawing as at F which reinforce the structural strength of the structure but form no part of the invention other than to function as a structural element in the illustrated preferred embodiment.

Following the convergent entry throat 12, the wires are deflected by a wire deflecting guide means shown in the form of a suction box 19 having a suction box cover 20. Downstream from the suction box, the wires pass over additional guide means as exemplified by a suction roll 18. Between the throat 12 and the roll 18, the wires are deflected laterally out of their paths so that instead of following the straight line between the throat and the roll 18, they follow a generally arcuate path. In following this arcuate path, the water in the stock is subjected to centrifugal force so that it is thrown outwardly as it follows the curved suction box cover 20. Water while passing over the arcuate path over the suction box cover 20 is also subjected to the suction within the box 19, and the cover 20 is perforate so that water will pass through the cover into the box 19. The suction within the box 19 is adjusted so that water in the brown layer of stock, adjacent the wire 10, passes into the suction box. A suction line 22 leads from the box 19, and a pump 21 drains water through the line 22 into a stock tank 23. Water in the white layer of stock, adjacent the wire 11, will be thrown centrifugally to the right into a water collection saveall 25. A skimmer blade 13 is located at the trailing end of the arcuate path of the cover 20 to skim water off the lower surface of the wire 11 directing it into the saveall 25.

The brown water which passes into the suction box 19 is mixed with additional stock formed from water and brown pulp in tank 23. The stock flows through a line 30 which leads from tank 23 to a headbox 29 through suitable pumping means such as a fan pump 31.

The white water obtained from the white stock is withdrawn from a saveall 25 by the pump 25b through a line 25a discharging into a chamber 26. This white water is carries through a line 27 to be mixed with fresh stock delivered by pumping means such as a fan pump 28 to the headbox 29. The chambers where the water from pumps 31 and 28 mix with the stock are not illustrated in detail but are shown schematically as will be appreciated by those skilled in the art.

The mechanism of the structure shown in the drawings is carried on suitable framework which need not be described in detail, and only a portion of the looped forming wires 10 and 11 are shown, and it will be understood that they are carried on suitable rolls and guides as exemplified by the rolls 16 and 17 for the forming wire 11. The web takeoff for wire 11 is also omitted from the drawing, but a pick-up roll and felt such as that known to the art is provided.

The stock is delivered through a jet stream 40 which is delivered into the throat 12 having the upper brown layer B and the lower white layer W. This is provided by a unitary headbox 29. The headbox has a slice chamber 32 which is shown as tapered and has slice walls with a lower pivotal slice wall 32a which may be controllably supported and moved by an arm 32b that controls the size of the slice opening 38. The slice walls connect to slice lips, each of which extend substantially the same distance toward the throat.

Upstream of the slice chamber 32, the headbox is divided into compartments 34 and 35 which are separated by a partition 33. Thus, the white stock is delivered to the headbox chamber 35, and the brown stock is delivered to the headbox chamber 34.

Separating the slice chamber and the compartments 34 and 35 is a cross-plate or wall 36 having openings 36a therethrough.

Within the slice chamber 32 are a plurality of trailing flexible elements 37. These elements uniquely and importantly function to maintain the flows from the two compartments 34 and 35 separate, yet retain the turbulence within the stock which is necessary for the proper formation of the web. While stock deliveries to the compartments 34 and 35 of the headbox are shown schematically, it will be understood that suitable headers are provided which maintain the agitation and turbulence in the stock to maintain the fibers in suspension. The turbulence or energy within the stock is maintained in the form of fine scale turbulence within the divided flow passages which are defined between the flexible trailing elements 37. These flexible elements are self-positionable, being affected only by the forces exerted thereon by the stock flowing toward the slice opening 38. These trailing flexible elements extend a substantial distance toward the slice opening so as to maintain the fine scale turbulence within the stock until it reaches the slice opening 38 and issues therefrom as a jet stream of two well-defined layers.

The flexible trailing elements are anchored only at their upstream ends and are spaced transversely of the stock flow stream. Their downstream portions are unattached, and they are formed of a flexible material such as plastic. The flexible elements 37 may additionally be tapered in their downstream directions so that their cross-sectional area becomes smaller. They may take various forms such as being circular, triangular, rectangular or slightly flattened in cross-section. If flat ribbons or strips are used, they preferably may extend in a cross-machine direction in the direction of the slice opening 38. In a preferred form the flexible elements 37 will take the form of sheets extending across the headbox and possibly slit or divided at spaced intervals.

Thus, it will be seen that there has been provided a multi-ply web forming mechanism wherein the water separated from the multiple layers is kept separate for reuse. Additionally, the layers are simultaneously formed for economy of space and time in the formation process. The simultaneous formation of the layers permits simultaneous separate individual dewatering of the layers despite the fact that they are in juxtaposition, and the dewatering mechanism is adapted to apply a dewatering force consistent with the characteristic of the stock of the ply. The arrangement makes possible the delivery of a multi-ply jet stream wherein the layers are integral, but separate.

FIG. 2 shows an arrangement for making a three ply web of paper. Using the principles of the invention, the mechanism is particularly well suited to making a web such as where the intermediate ply has a high ash content and the outer plies are long wood fibers so as to prevent the escape of the high ash material from the pulp in the intermediate layer during dewatering. The mechanism of FIG. 2 has looped twin forming wires 41 and 42 trained over breast rolls 43 and 44 so as to form a throat 45 for receiving stock emitted from a headbox 46.

The headbox is provided with a main chamber which leads to a slice chamber having a slice opening 48. The headbox is divided into three compartments with an intermediate compartment 47 and outer compartments 50 and 51. Headbox divider walls 48 and 49 extend across and through the headbox to form the compartments. These compartments are separated for the full length of the slice chamber by trailing flexible wall elements 53 and 54 which extend substantially to the slice opening 48. The flexible elements are of plastic or similar flexible material and extend for the full width of the slice chamber so as to be selfpositionable by the opposing hydraulic pressures of the stock in the chambers and to maintain the different layers of stock separate in their flow to the slice opening 48.

In each of the separate compartments of the slice chamber there are located flexible trailing elements such as 55 and 57 for the outer chambers of the slice chamber and 56 for the intermediate chamber. The flexible trailing elements may have the same construction as the divider sheet elements 52 and 53 or they may be separate such as individual wires or filaments. They are each anchored at their upstream ends with their downstream ends unattached so as to be self-positionable due to the hydraulic forces of the fluid flowing through the chamber. Thus, a fine scale turbulence is maintained within the layers of stock in each of the respective chambers due both to the individual trailing elements in each of the chambers and the dividing chamber walls which are flexible sheet elements. The flexible sheet elements extend fully to the slice opening 48 whereas the individual elements in each of the chambers need not extend that far. They, however, extend substantially to the slice opening, but are stopped sufficiently short so that they do not crowd the reduced crosssectional area of the slice opening. They may be of varying length with certain of them extending fully to the slice opening and others stopping short of the slice opening.

In the outer layers, long fibered stock is used and stock delivery means shown at 60 and 61 for the outer chambers 51 and 50 are provided. The intermediate layer is provided with a stock supply 62 which delivers a high ash content stock. Because the three layers of stock are delivered simultaneously and are not intermixed prior to emerging from the slice opening, the intermediate high ash content layer will dewater outwardly through the two outer layers, and the long fibered stocks will prevent the draining of ash as has occurred with structures heretofore available. The resultant paper web is shown in FIG. 3 with outer layers 65 and 66 of long wood fibers and the intermediate layer 67 being of a high ash content for adding stiffness and the other properties which a high ash content web possesses.

FIG. 4 shows somewhat schematically, but in greater detail, a headbox arrangement wherein three separate stocks are supplied to chambers 71, 72 and 73 leading to the headbox. A plate 74 extends across the headbox with openings therethrough which lead to diffuser tubes such as 75. The tubes 75 for each of the headbox chambers are similar in construction and, therefore, only one need be described. The tubes have an upstream smaller end 75a leading to an expanding portion 75b which leads to a larger section 75c of constant dimension that opens through openings in a plate 76. The plate extends across the headbox and has openings which open to a tapered portion of the headbox having outer walls 79 and 80. In this tapered portion of the headbox are divider plates 77 and 78 dividing the headbox into chambers 81, 82 and 83. The plates 77 and 78 extend continuously across the entire width of the headbox and extend in the direction of flow so as to provide separate chambers.

The separating plates 77 and 78 are mounted at their upstream ends to the plate 76, and at their downstream ends to a plate 84 which extends across the headbox and has openings such as 84a extending therethrough. The stock flows through the plate and enters a tapered slice chamber formed between walls 87 and 88 which extend toward each other to form the tapered slice chamber, and between their distal ends 91 and 92 form a slice opening 90. The slice chamber is divided into compartments which are extensions of the compartments 81, 82 and 83 of the headbox and are formed by flexible trailing sheet elements 85 and 86 which are in alignment with the plates 77 and 78 and which extend all the way to the slice opening 90. The elements 85 and 86 form outer slice chamber compartments or chambers 94 and 96 and an intermediate chamber 95. Within each of the slice chamber compartments are additional selfpositionable trailing elements 97, 98 and 99. These may be the same as the sheet elements 85 and 86, or they may be separate strand-like elements, but all are supported at their upstream ends with their downstream ends being unsupported so as to be self-positionable due to the hydraulic forces of the stock flowing toward the slice. The slice opening 90 is adjustable in size by the upper slice chamber wall 87 which is pivoted at its upper edge on a hinge joint 89. A rod 93 pivots the upper slice chamber wall. The stock passes through the slice opening 90 onto a forming surface, not shown. Stock having different characteristics is delivered to the separate delivery chambers 71, 72 and 73 at the upstream end of the headbox, and these chambers may be tapered across the headbox so as to insure uniform flow across the width of the headbox. The outer layers which are delivered to the outer chambers such as 71 and 73 may be long fibered stock similar to the arrangement described in connection with FIG. 2 with the intermediate chamber 72 receiving high ash content stock. Other combinations of stocks may be employed dependent upon the type of multi-ply paper to be formed. A continual separation of the different types of stock is maintained fully to the slice opening 90, but pressures between the layers of stock are maintained uniform because of the flexible elements, and the flexible elements maintain uniform fine scale turbulence and do not induce large scale turbulence or voids which would disrupt the uniform formation of the stock layers on the forming surface.

Claims

I claim as my invention:

1. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier, the combination comprising:

a headbox having a lower wall and an upper wall;

a slice chamber connected to the headbox having a lower slice wall and an upper slice wall being extensions of the headbox walls, one of said slice walls being pivoted at its upstream edge with said slice walls tapered toward each other and terminating in a slice opening;

flow divider plates in the headbox extending completely across the headbox in the direction of flow and dividing the headbox into separate stock chambers;

separate stock supply means to each of said chambers for delivering stocks of different physical characteristics;

flexible sheet members in the slice chamber secured at their upstream ends in alignment with the plates with their downstream ends being unattached and extending to the slice opening whereby the stocks of the separate chambers do not intermix and remain separate for the full travel onto the forming surface and the pressure of the stock flows on opposite sides of said sheet members remains equal for uniform velocity flow at the slice opening;

and a forming surface positioned to have stock discharged thereon from the slice opening.

2. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 1:

wherein the forming surface is formed of a pair of looped traveling forming wires with guides therein arranged to form a forming throat into which the stock is discharged followed by a forming run.

3. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 1:

including a plurality of flexible self-positionable trailing members in each chamber of the slice chamber and terminating upstream from the flexible sheet members in the slice chamber.

4. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier, the combination comprising:

a foraminous forming surface for receiving a liquid stock and dewatering the stock;

a headbox having a slice chamber formed by slice walls terminating in slice lips which form a slice opening for directing a jet stream onto the forming surface; said slice lips extending substantially the same distance toward said surface; said headbox also having a preslice chamber immediately upstream of the slice chamber; a first rigid partition extending across said preslice chamber dividing the preslice chamber into multiple stock chambers;

a second partition extending across said slice chamber forming a continuation of said first partition and dividing the slice chamber into multiple stock chambers to extend to the slice opening; said second partition being supported only at its upstream end with its downstream portion unattached and constructed to be self-positionable so as to be responsive to forces exerted thereon by the stock flowing toward the slice so that the stocks from the multiple chambers exit through the slice opening at uniform velocity;

and means for supplying stocks of different characteristics to each of said multiple stock chambers in the preslice chamber.

5. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 4:

wherein said forming surface is comprised of a first looped traveling forming wire and a second looped traveling forming wire;

and guide means within said wires guiding the wires to provide a forming throat receiving stock from said slice followed by a forming run between the wires.

6. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 4:

including a third partition extending across said preslice chamber so that the headbox is divided into at least three stock chambers comprising two outer chambers and one intermediate chamber and including a fourth partition being a continuance of the third partition which extends to the slice opening and is self-positioning.

7. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 6:

including means for delivering stock having long fibers to each of the outer chambers of the headbox;

and means for delivering stock having a high ash content to the intermediate chamber of the headbox.

8. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 4:

wherein the slice chamber is tapered and each of the multiple stock chambers of the slice chamber contains a plurality of flexible self-positionable trailing elements anchored at their upstream ends with their downstream ends being self-positionable by the pressures of the stock flowing through the slice chamber.

9. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 8:

wherein each of said trailing elements is tapered and is thicker at its upstream end than the downstream end.

10. In a machine for making a multi-ply web such as a paper from stocks having a slurry of fibers in a liquid carrier constructed in accordance with claim 8:

wherein each of said flexible elements is in the form of a continuous sheet extending fully across the width of the slice chamber.