Fourdrinier paper-making machine with water-control base wire positioned beneath forming wire
United States Patent 3876500
A Fourdrinier wire travels in a predetermined path, and a stock inlet discharges aqueous paper stock onto this wire. A travelling base wire has a first stringer arranged to travel underneath and in contact with the Fourdrinier wire, and a second stringer arranged to travel out of contact therewith. The base wire is so constituted or of such material as to attract water from the Fourdrinier wire by capillary action, such as a felt or a synthetic plastic wire of close-meshed construction. An adjusting arrangement including a spray tube and suction box acts upon the second stringer to permit adjustment of the content of water in the base wire.
US Patent References:
Felt cleaner
Sheahan - February 1925 - 1526094
Paper-making machine
Danninger - March 1926 - 1577897
Apparatus for and method of making paper
Reimer - January 1936 - 2028952
Felt cleaner
Sheahan - February 1925 - 1526094
Paper-making machine
Danninger - March 1926 - 1577897
Apparatus for and method of making paper
Reimer - January 1936 - 2028952
Inventors:
Csordas, Elemer (Heindenheim, DT)
Egelhof, Dieter (Heindenheim, DT)
Egelhof, Dieter (Heindenheim, DT)
Application Number:
05/352314
Publication Date:
04/08/1975
Filing Date:
04/19/1973
View Patent Images:
Export Citation:
Assignee:
Veith J. M. G. M. B. H. (Brenz, DT)
Primary Class:
Other Classes:
162/351, 162/300, 162/211, 162/278
International Classes:
D21F1/52; D21F9/02; D21F1/48; D21F9/00; D21F1/32; D21F1/00; D21F1/10
Field of Search:
162/348,211,351,303,DIG.1,298,274,278,300
Primary Examiner:
Bashore, Leon S.
Assistant Examiner:
Tushin, Richard H.
Attorney, Agent or Firm:
Striker, Michael S.
Claims:
1. In a Fourdrinier paper-making machine, a combination comprising a Fourdrinier wire travelling in a path; a stock inlet for discharging aqueous paper stock onto said Fourdrinier wire; a travelling base wire means having a first stringer arranged to travel in contact with said Fourdrinier wire along a portion of said path which has an upstream and downstream end, and a second stringer arranged to travel out of contact with said Fourdrinier wire, said base wire means being operative for withdrawing water from said Fourdrinier wire by capillary action and for storing the thus withdrawn water within itself; deflecting means for deflecting said first stringer intermediate said ends first out of and thereupon back into engagement with said Fourdrinier wire; means for removing water from said first stringer while the same is out of engagement with said Fourdrinier wire; and adjusting means acting upon said second stringer for adjusting the content of water in said base wire
2. A combination as defined in claim 1; further comprising a breast roller about which said Fourdrinier wire and said first stringer of said base wire means are both trained; and wherein said stock inlet is arranged to discharge said stock onto said Fourdrinier wire in the region of said
3. A combination as defined in claim 1, wherein said base wire means is a
4. A combination as defined in claim 1, wherein said base wire means is a
5. A combination as defined in claim 1; and further comprising supporting means arranged adjacent said portion of said path for supporting said wires, and having means forming at least one suction chamber for
6. A combination as defined in claim 1; and further comprising means arranged at a downstream end of said portion of said path, in engagement with said base wire means for deflecting the same away from said
7. A combination as defined in claim 1; and further comprising a deflecting portion arranged at said downstream end of said portion of said path, and having a guide surface which engages said base wire means and is oriented
8. A combination as defined in claim 7; and further comprising support means arranged adjacent said portion of said path for supporting said
9. A combination as defined in claim 8, wherein said guide surface is
10. A combination as defined in claim 1; further comprising a breast roller around which said Fourdrinier wire and said base wire means are both trained, and wherein said stock inlet discharges onto said Fourdrinier wire in the region of said breast roller; and at least one additional breast roller, at least one additional Fourdrinier wire, at least one additional base wire means trained with said additional Fourdrinier wire about said additional breast roller, and additional adjusting means acting upon the second stringer of said additional base wire means for adjusting
11. A combination as defined in claim 10; and means maintaining each first stringer of the respective base wire is in contact with the associated Fourdrinier wire from the respective breast roller to a location downstream of the latter beyond which the fibers of said stock no longer appreciably change their relative positions during de-watering.
2. A combination as defined in claim 1; further comprising a breast roller about which said Fourdrinier wire and said first stringer of said base wire means are both trained; and wherein said stock inlet is arranged to discharge said stock onto said Fourdrinier wire in the region of said
3. A combination as defined in claim 1, wherein said base wire means is a
4. A combination as defined in claim 1, wherein said base wire means is a
5. A combination as defined in claim 1; and further comprising supporting means arranged adjacent said portion of said path for supporting said wires, and having means forming at least one suction chamber for
6. A combination as defined in claim 1; and further comprising means arranged at a downstream end of said portion of said path, in engagement with said base wire means for deflecting the same away from said
7. A combination as defined in claim 1; and further comprising a deflecting portion arranged at said downstream end of said portion of said path, and having a guide surface which engages said base wire means and is oriented
8. A combination as defined in claim 7; and further comprising support means arranged adjacent said portion of said path for supporting said
9. A combination as defined in claim 8, wherein said guide surface is
10. A combination as defined in claim 1; further comprising a breast roller around which said Fourdrinier wire and said base wire means are both trained, and wherein said stock inlet discharges onto said Fourdrinier wire in the region of said breast roller; and at least one additional breast roller, at least one additional Fourdrinier wire, at least one additional base wire means trained with said additional Fourdrinier wire about said additional breast roller, and additional adjusting means acting upon the second stringer of said additional base wire means for adjusting
11. A combination as defined in claim 10; and means maintaining each first stringer of the respective base wire is in contact with the associated Fourdrinier wire from the respective breast roller to a location downstream of the latter beyond which the fibers of said stock no longer appreciably change their relative positions during de-watering.
Description:
BACKGROUND OF THE INVENTION
The present invention relates generally to paper-making machines, and more particularly to a Fourdrinier paper-making machine.
Fourdrinier paper making machines are well known both as to their construction and operation and are not believed to require a detailed discussion. It is known to those conversant with this field of art that in machines of this type a severe and sudden increase in suction pressure will develop at certain locations, for instance in the run-off nip of the breast roll or on the de-watering elements adjoining the same. This interferes with the uniform deposition of fibers from the aqueous paper stock onto the Fourdrinier wire, which is a screen, and thus leads to the formation of paper of poor quality and undesirable porosity. In fact, the porosity may be so pronounced that the paper is formed with small pinholes. Supporting means which are conventionally provided for the Fourdrinier wire will also result in the development of locations wherein the pressure will suddenly change, with the result that these pressure surges also will adversely affect the formation of paper on the Fourdrinier wire.
The problem is known to the industry and various attempts have been made to overcome it. In particular, it has been attempted to provide either water-impermeable or else water-flooded bench supports for the Fourdrinier wire which were so arranged as to help prevent the development of adverse pressure peaks at the beginning of the paper-forming zone on the wire. However, in actual fact this has not been as successful as was hoped because de-watering of the aqueous paper stock deposited on the Fourdrinier wire cannot take place where these benches are provided, so that the actual formation of paper on the wire will then begin only downstream of these benches and will still be affected by pressure surges which take place downstream of the benches.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to avoid the aforementioned disadvantages.
More particularly it is an object of the present invention to provide an improved Fourdrinier paper-making machine which is not possessed of these disadvantages.
In particular, it is an object of the invention to avoid the detrimental sudden pressure changes in the de-watering pressure which take place in the zone where the paper is being formed on the Fourdrinier wire, so that there will be a uniform action of the forces which result in the de-watering process.
Another object of the present invention is to provide such an improved machine wherein the quantity of water removed from the stock on the Fourdrinier wire is selectable and adjustable at will.
In keeping with the above objects, and others which will become apparent hereafter, one feature of the invention resides, in a Fourdrinier paper-making machine, in a combination comprising a Fourdrinier wire travelling in a path, and a stock inlet for admitting aqueous paper stock onto the Fourdrinier wire. A travelling base wire is provided, having a first stringer arranged to travel in contact with the Fourdrinier wire along a portion of the path, and a second stringer arranged to travel out of contact with the Fourdrinier wire. The base wire is so constituted as to attract water from the Fourdrinier wire by capillary action. Adjusting means acts upon the second stringer for adjusting the content of water in the base wire.
Resort to the present invention makes it possible to produce paper which is exceptionally uniform in its structure, and which is largely free of porous areas and pinholes. This is highly advantageous, not only in general but in particular where very thin papers are to be produced, such as papers used in the production of capacitors or cigarette papers. The demand for freedom from pinholes and for uniformity of the paper thickness is particularly stringent in this type of paper.
The invention largely eliminates the effect on pressure surges of any supporting means which may be disposed either under the Fourdrinier wire or under the base wire, so that any pressure peaks which may occur at locations where such supporting means is present will no longer act on the developing paper layer on the Fourdrinier wire with such effect as to cause irregularities, porosity or the formation of pinholes in the paper.
If the base wire is already substantially saturated with water at the location at which the aqueous paper stock contacts the Fourdrinier wire, then the fibers in the stock will settle only slowly on the Fourdrinier wire due to the reduction in the rate at which water passes through the Fourdrinier wire. Such reduction is, of course, the result of the fact that the base wire is capable of attracting only little or no water by capillary action, owing to its saturated or near-saturated state. Conversely, if the base wire is relatively less saturated, then the formation of the paper material on the Fourdrinier wire will be accelerated, because the base wire then obviously is able to take up a larger quantity of water from the aqueous paper stock, that is water which passes through the Fourdrinier wire, and it is able to do so faster than otherwise. Thus, the de-watering characteristics in their entirety can be influenced by appropriate adjustment of the water content of the base wire, for which purpose the adjusting means according to the present invention is provided.
The use of a base wire in conjunction with a Fourdrinier wire is not entirely unknown. The use of such a base wire has been proposed in the prior art, but not for the purposes of the present invention. Instead, such a base wire was intended as a protection for the Fourdrinier wire and was neither intended to nor capable of influencing the de-watering operation. In fact, it was disposed outside the first de-watering zone which begins directly at the stock inlet, and it was not capable of attracting water by capillary action, nor were there adjusting means provided for adjusting the water content of the base wire. This is not surprising because there was no water content, owing to a lack of capillary-attraction capability, and due to the fact that the concept according to the present invention was not invisioned in the prior art.
In a paper-making machine in which the stock inlet discharges onto the Fourdrinier wire in the region of a breast roll, the base wire will pass around the breast roll together with the Fourdrinier wire.
The base wire may, according to the present invention, be in form of a felt material which is capable of exerting relatively significant capillary forces upon the water of the aqueous paper stock deposited on the Fourdrinier wire. Moreover, such material has, of course, a relatively large water-absorption capacity which insures very adequate control of the de-watering of the paper web which is being formed on the Fourdrinier wire.
However, the invention also contemplates the use of a web of synthetic plastic fabric as the base wire, if the fabric has a sufficiently close-meshed construction and adequate thickness to permit capillary forces to act, and to provide an adequate water storage capability.
Evidently, the invention may be embodied in a paper-making machine having one, two or more Fourdrinier wires, each of which is associated with a stock inlet.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary diagrammatic view illustrating a detail of a Fourdrinier paper-making machine according to one embodiment of the invention;
FIG. 2 is a view analogous to FIG. 1 but illustrating a further embodiment of the invention; and
FIG. 3 is a view similar to FIG. 2 but illustrating an additional embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In all three Figures only those portions of a Fourdrinier paper-making machine have been illustrated, which are essential for an understanding of the present invention. All other elements have been omitted because they are well known per se and not required for understanding the concept and operation of the invention.
With this in mind, and discussing firstly the embodiment in FIG. 1 which will be seen to be concerned with a Fourdrinier paper-making machine having a single Fourdrinier wire, it will be seen that the Fourdrinier wire is designated with reference numeral 1 and advances in the direction indicated by its associated arrow. It is trained around a breast roll 2 and in the zone of this roll a stock inlet 3 is provided which discharges onto the Fourdrinier wire 1 an aqueous paper stock, that is an aqueous fiber suspension. A base wire 4 is provided which also passes around the breast roll 3 underneath the Fourdrinier wire 1, with which one of the stringers of the base wire 4 is in contact so as to move therewith. The aforementioned stringer continues to move with the Fourdrinier wire 1 in the path of the latter until the end of the sheet-forming zone (the zone in which paper sheet is formed on the Fourdrinier wire 1) is reached. The end of the sheet-forming zone is intended to designate the region at which the relative position of the fibers on the Fourdrinier wire 1 will no longer substantially alter with progressive de-watering.
Adjusting means is provided and acts upon the other stringer of the base wire 4, that is that stringer which is not in contact with the Fourdrinier wire 1. The adjusting means serve to adjust and control the water content of the base wire 4, utilizing a suction box 5 and a spray tube 6 which are positioned relative to the base wire 4 in the manner illustrated in FIG. 1.
To facilitate removal of the fine fraction of matter which is carried along by the water removed from the Fourdrinier wire 1, a further suction box 7 is provided to act upon the stringer of the base wire 4 which is not in contact with the Fourdrinier wire 1. A suction box 7 acts upon that side of the base wire 4 which has previously been in engagement with the Fourdrinier wire 1 to remove the fine fraction.
It will be seen that the base wire 4 and the Fourdrinier wire 1 are guided together in the region between the breast roll 2 and their point of separation, over supporting means 8 which may have a plurality of boxes into which further water from the Fourdrinier wire can run off. The free stringer of the base wire 4, that is the stringer which is not in contact with the Fourdrinier wire 1, passes over a plurality of guide rollers 9, and a guide portion 10 having a guide surface, which may be integrally formed with the supporting means 8, is provided at the location where the contacting stringer of the base wire 4 separates from the Fourdrinier wire 1.
As mentioned earlier, the base wire 4 may be a felt web, or it may be a web of synthetic plastic textile material of appropriate thickness and of a mesh which is sufficiently fine to provide for the desired capillary action. Of course, in any case the material of the base wire 4 must be capable of storing that amount of attracted water which it is anticipated will be removed by the base wire from the stock on the Fourdrinier wire.
Coming to the embodiment of FIG. 2 it will be seen that here in this Figure there are provided two substantially identical Fourdrinier wires 1, each of which corresponds to the wire 1 of FIG. 1. A guide roller 11 is provided at the region where the base wire 4 associated with one of the Fourdrinier wires 1 (the right-hand one) separates from the latter. In the region where the base wire 4 associated with the other Fourdrinier wire 1 (the left-hand one) separates from the same, there is provided a guide element 12 which, unlike the embodiment of FIG. 1, is separate from the supporting means 8. Each of the Fourdrinier wires 1 in this embodiment is provided with its own stock inlet 3, and the direction of advancement of the Fourdrinier wires 1 (which again corresponds to the direction of advancement of the respective base wires 4) is indicated by their associated arrows.
The adjusting means here may again be in form of the suction boxes 5 and spray conduits 6, or it may be replaced with pressure rollers 13, or both these measures may be utilized in conjunction with one another.
FIG. 3, finally, shows a further embodiment wherein the contacting stringer of the base wire 4 is guided away from the Fourdrinier wire 1 by the guide portion 10 of the supporting means 8 at one location, to move past a suction box 7 which is thus seen to be located downstream of a first de-watering region. The base wire 4 is thereupon guided around guide roller 9 and reversing roller 13 back into engagement with the Fourdrinier wire 1, to define with the same a second de-watering region, to be finally guided away again from the Fourdrinier wire 1 by the guide portion 10 of the second illustrated support means 8. It then passes over another suction box 7 and the free noncontacting stringer then again is subjected to adjustment of its water content which was attracted by capillar action, by the adjusting means 5,6. One of the guide rollers 9 in this as in the preceeding embodiments may be constructed as a driving roller for the base wire 4, in which case a separate cooperating nip roller may be provided which cooperates with the driving roller.
It is also possible for the base wire to surround the suction roller of the machine (not illustrated, being located towards the left in FIG. 3) together with the Fourdrinier wire 1, before it finally becomes separated from the latter. The necessary degree of de-watering for the deposited paper on the Fourdrinier wire 1 will nevertheless be obtained in such condition, due to the interposed suction box 7 located downstream of the first but upstream of the second de-watering section.
In all of the illustrated embodiments the base wire 4 is shown as surrounding the breast roll 2, together with the Fourdrinier wire 1. However, it should be understood that it is also possible and within the intention of the present invention that the base wire 4 be guided in contact with the Fourdrinier wire 1 only downstream of the breast roll 2. In this case, however, the stock inlet 3 is then not arranged in the region of the breast roll, but only in that region where the Fourdrinier wire 1 and the base wire 4 are in contact with each other.
Resort to the present invention avoids the disadvantages which were outlined earlier with respect to the prior art, and makes it possible to produce not only single-ply papers, but in particular to produce multi-ply papers whose individual plies are formed with a high degree of accuracy and freedom from porosity and pinholes, so that the thus-produced multi-ply paper has a high degree of uniformity and low porosity, conditions which are most desirable.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
While the invention has been illustrated and described as embodied in a Fourdrinier paper-making machine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
The present invention relates generally to paper-making machines, and more particularly to a Fourdrinier paper-making machine.
Fourdrinier paper making machines are well known both as to their construction and operation and are not believed to require a detailed discussion. It is known to those conversant with this field of art that in machines of this type a severe and sudden increase in suction pressure will develop at certain locations, for instance in the run-off nip of the breast roll or on the de-watering elements adjoining the same. This interferes with the uniform deposition of fibers from the aqueous paper stock onto the Fourdrinier wire, which is a screen, and thus leads to the formation of paper of poor quality and undesirable porosity. In fact, the porosity may be so pronounced that the paper is formed with small pinholes. Supporting means which are conventionally provided for the Fourdrinier wire will also result in the development of locations wherein the pressure will suddenly change, with the result that these pressure surges also will adversely affect the formation of paper on the Fourdrinier wire.
The problem is known to the industry and various attempts have been made to overcome it. In particular, it has been attempted to provide either water-impermeable or else water-flooded bench supports for the Fourdrinier wire which were so arranged as to help prevent the development of adverse pressure peaks at the beginning of the paper-forming zone on the wire. However, in actual fact this has not been as successful as was hoped because de-watering of the aqueous paper stock deposited on the Fourdrinier wire cannot take place where these benches are provided, so that the actual formation of paper on the wire will then begin only downstream of these benches and will still be affected by pressure surges which take place downstream of the benches.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to avoid the aforementioned disadvantages.
More particularly it is an object of the present invention to provide an improved Fourdrinier paper-making machine which is not possessed of these disadvantages.
In particular, it is an object of the invention to avoid the detrimental sudden pressure changes in the de-watering pressure which take place in the zone where the paper is being formed on the Fourdrinier wire, so that there will be a uniform action of the forces which result in the de-watering process.
Another object of the present invention is to provide such an improved machine wherein the quantity of water removed from the stock on the Fourdrinier wire is selectable and adjustable at will.
In keeping with the above objects, and others which will become apparent hereafter, one feature of the invention resides, in a Fourdrinier paper-making machine, in a combination comprising a Fourdrinier wire travelling in a path, and a stock inlet for admitting aqueous paper stock onto the Fourdrinier wire. A travelling base wire is provided, having a first stringer arranged to travel in contact with the Fourdrinier wire along a portion of the path, and a second stringer arranged to travel out of contact with the Fourdrinier wire. The base wire is so constituted as to attract water from the Fourdrinier wire by capillary action. Adjusting means acts upon the second stringer for adjusting the content of water in the base wire.
Resort to the present invention makes it possible to produce paper which is exceptionally uniform in its structure, and which is largely free of porous areas and pinholes. This is highly advantageous, not only in general but in particular where very thin papers are to be produced, such as papers used in the production of capacitors or cigarette papers. The demand for freedom from pinholes and for uniformity of the paper thickness is particularly stringent in this type of paper.
The invention largely eliminates the effect on pressure surges of any supporting means which may be disposed either under the Fourdrinier wire or under the base wire, so that any pressure peaks which may occur at locations where such supporting means is present will no longer act on the developing paper layer on the Fourdrinier wire with such effect as to cause irregularities, porosity or the formation of pinholes in the paper.
If the base wire is already substantially saturated with water at the location at which the aqueous paper stock contacts the Fourdrinier wire, then the fibers in the stock will settle only slowly on the Fourdrinier wire due to the reduction in the rate at which water passes through the Fourdrinier wire. Such reduction is, of course, the result of the fact that the base wire is capable of attracting only little or no water by capillary action, owing to its saturated or near-saturated state. Conversely, if the base wire is relatively less saturated, then the formation of the paper material on the Fourdrinier wire will be accelerated, because the base wire then obviously is able to take up a larger quantity of water from the aqueous paper stock, that is water which passes through the Fourdrinier wire, and it is able to do so faster than otherwise. Thus, the de-watering characteristics in their entirety can be influenced by appropriate adjustment of the water content of the base wire, for which purpose the adjusting means according to the present invention is provided.
The use of a base wire in conjunction with a Fourdrinier wire is not entirely unknown. The use of such a base wire has been proposed in the prior art, but not for the purposes of the present invention. Instead, such a base wire was intended as a protection for the Fourdrinier wire and was neither intended to nor capable of influencing the de-watering operation. In fact, it was disposed outside the first de-watering zone which begins directly at the stock inlet, and it was not capable of attracting water by capillary action, nor were there adjusting means provided for adjusting the water content of the base wire. This is not surprising because there was no water content, owing to a lack of capillary-attraction capability, and due to the fact that the concept according to the present invention was not invisioned in the prior art.
In a paper-making machine in which the stock inlet discharges onto the Fourdrinier wire in the region of a breast roll, the base wire will pass around the breast roll together with the Fourdrinier wire.
The base wire may, according to the present invention, be in form of a felt material which is capable of exerting relatively significant capillary forces upon the water of the aqueous paper stock deposited on the Fourdrinier wire. Moreover, such material has, of course, a relatively large water-absorption capacity which insures very adequate control of the de-watering of the paper web which is being formed on the Fourdrinier wire.
However, the invention also contemplates the use of a web of synthetic plastic fabric as the base wire, if the fabric has a sufficiently close-meshed construction and adequate thickness to permit capillary forces to act, and to provide an adequate water storage capability.
Evidently, the invention may be embodied in a paper-making machine having one, two or more Fourdrinier wires, each of which is associated with a stock inlet.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary diagrammatic view illustrating a detail of a Fourdrinier paper-making machine according to one embodiment of the invention;
FIG. 2 is a view analogous to FIG. 1 but illustrating a further embodiment of the invention; and
FIG. 3 is a view similar to FIG. 2 but illustrating an additional embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In all three Figures only those portions of a Fourdrinier paper-making machine have been illustrated, which are essential for an understanding of the present invention. All other elements have been omitted because they are well known per se and not required for understanding the concept and operation of the invention.
With this in mind, and discussing firstly the embodiment in FIG. 1 which will be seen to be concerned with a Fourdrinier paper-making machine having a single Fourdrinier wire, it will be seen that the Fourdrinier wire is designated with reference numeral 1 and advances in the direction indicated by its associated arrow. It is trained around a breast roll 2 and in the zone of this roll a stock inlet 3 is provided which discharges onto the Fourdrinier wire 1 an aqueous paper stock, that is an aqueous fiber suspension. A base wire 4 is provided which also passes around the breast roll 3 underneath the Fourdrinier wire 1, with which one of the stringers of the base wire 4 is in contact so as to move therewith. The aforementioned stringer continues to move with the Fourdrinier wire 1 in the path of the latter until the end of the sheet-forming zone (the zone in which paper sheet is formed on the Fourdrinier wire 1) is reached. The end of the sheet-forming zone is intended to designate the region at which the relative position of the fibers on the Fourdrinier wire 1 will no longer substantially alter with progressive de-watering.
Adjusting means is provided and acts upon the other stringer of the base wire 4, that is that stringer which is not in contact with the Fourdrinier wire 1. The adjusting means serve to adjust and control the water content of the base wire 4, utilizing a suction box 5 and a spray tube 6 which are positioned relative to the base wire 4 in the manner illustrated in FIG. 1.
To facilitate removal of the fine fraction of matter which is carried along by the water removed from the Fourdrinier wire 1, a further suction box 7 is provided to act upon the stringer of the base wire 4 which is not in contact with the Fourdrinier wire 1. A suction box 7 acts upon that side of the base wire 4 which has previously been in engagement with the Fourdrinier wire 1 to remove the fine fraction.
It will be seen that the base wire 4 and the Fourdrinier wire 1 are guided together in the region between the breast roll 2 and their point of separation, over supporting means 8 which may have a plurality of boxes into which further water from the Fourdrinier wire can run off. The free stringer of the base wire 4, that is the stringer which is not in contact with the Fourdrinier wire 1, passes over a plurality of guide rollers 9, and a guide portion 10 having a guide surface, which may be integrally formed with the supporting means 8, is provided at the location where the contacting stringer of the base wire 4 separates from the Fourdrinier wire 1.
As mentioned earlier, the base wire 4 may be a felt web, or it may be a web of synthetic plastic textile material of appropriate thickness and of a mesh which is sufficiently fine to provide for the desired capillary action. Of course, in any case the material of the base wire 4 must be capable of storing that amount of attracted water which it is anticipated will be removed by the base wire from the stock on the Fourdrinier wire.
Coming to the embodiment of FIG. 2 it will be seen that here in this Figure there are provided two substantially identical Fourdrinier wires 1, each of which corresponds to the wire 1 of FIG. 1. A guide roller 11 is provided at the region where the base wire 4 associated with one of the Fourdrinier wires 1 (the right-hand one) separates from the latter. In the region where the base wire 4 associated with the other Fourdrinier wire 1 (the left-hand one) separates from the same, there is provided a guide element 12 which, unlike the embodiment of FIG. 1, is separate from the supporting means 8. Each of the Fourdrinier wires 1 in this embodiment is provided with its own stock inlet 3, and the direction of advancement of the Fourdrinier wires 1 (which again corresponds to the direction of advancement of the respective base wires 4) is indicated by their associated arrows.
The adjusting means here may again be in form of the suction boxes 5 and spray conduits 6, or it may be replaced with pressure rollers 13, or both these measures may be utilized in conjunction with one another.
FIG. 3, finally, shows a further embodiment wherein the contacting stringer of the base wire 4 is guided away from the Fourdrinier wire 1 by the guide portion 10 of the supporting means 8 at one location, to move past a suction box 7 which is thus seen to be located downstream of a first de-watering region. The base wire 4 is thereupon guided around guide roller 9 and reversing roller 13 back into engagement with the Fourdrinier wire 1, to define with the same a second de-watering region, to be finally guided away again from the Fourdrinier wire 1 by the guide portion 10 of the second illustrated support means 8. It then passes over another suction box 7 and the free noncontacting stringer then again is subjected to adjustment of its water content which was attracted by capillar action, by the adjusting means 5,6. One of the guide rollers 9 in this as in the preceeding embodiments may be constructed as a driving roller for the base wire 4, in which case a separate cooperating nip roller may be provided which cooperates with the driving roller.
It is also possible for the base wire to surround the suction roller of the machine (not illustrated, being located towards the left in FIG. 3) together with the Fourdrinier wire 1, before it finally becomes separated from the latter. The necessary degree of de-watering for the deposited paper on the Fourdrinier wire 1 will nevertheless be obtained in such condition, due to the interposed suction box 7 located downstream of the first but upstream of the second de-watering section.
In all of the illustrated embodiments the base wire 4 is shown as surrounding the breast roll 2, together with the Fourdrinier wire 1. However, it should be understood that it is also possible and within the intention of the present invention that the base wire 4 be guided in contact with the Fourdrinier wire 1 only downstream of the breast roll 2. In this case, however, the stock inlet 3 is then not arranged in the region of the breast roll, but only in that region where the Fourdrinier wire 1 and the base wire 4 are in contact with each other.
Resort to the present invention avoids the disadvantages which were outlined earlier with respect to the prior art, and makes it possible to produce not only single-ply papers, but in particular to produce multi-ply papers whose individual plies are formed with a high degree of accuracy and freedom from porosity and pinholes, so that the thus-produced multi-ply paper has a high degree of uniformity and low porosity, conditions which are most desirable.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
While the invention has been illustrated and described as embodied in a Fourdrinier paper-making machine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.