PAPER MACHINE FOR THE MANUFACTURE OF HIGH BULK SOFT CREPE PAPER

Abstract: A paper machine for the manufacture of a soft crepe paper grade, which in respect of bulk and softness is fully comparable to the one manufactured in a paper machine made for through-air drying by hot air, is in principle a conventional soft crepe paper machine, in which a conveying and imprinting fabric (25) is substituted for the pick-up felt. A pick-up device (23) operating with air flow picks up the web (15) from the forming fabric (9) and transfers it to the imprinting fabric (25) without any appreciable compaction of the web (15). The imprinting fabric (25) is maintained clean and dry by cleaning devices (41, 43, 45) and a device (47) for depleting the imprinting fabric (25) of water before it arrives at the pick-up device (23). Further, air current generating devices (35, 37, 39) are provided for removing water from the paper web (15) by passing air of ambient temperature through the web (15). These have a capacity that is sufficient for raising the dry solids content of the web to at least 25 % before the web arrives at the Yankee dryer (29). If desired, the paper machine may easily and in a short time be converted into a conventional soft crepe paper machine, essentially by substituting a pick-up felt for the imprinting fabric (25).

Description: Paper Machine for the Manufacture of High Bulk Soft Crepe Paper Technical Field The present invention relates to a paper machine for the manufacture of soft crepe paper and including a wire section, which has at least one forming fabric loop for forming a paper web, and a drying section in¬ cluding a Yankee dryer, in which drying section the paper web is dried, said paper machine having a first operative design for the manufacture of soft crepe paper having certain measurements of bulk and softness, in which first operative design a press section located between the wire section and the drying section has a felt movable in an endless loop and arranged to run from a pick-up device located at a transition be¬ tween the wire section and the press section to a press roll forming a nip with the Yankee dryer while carrying the paper web on its under side, the carrying forming fabric being arranged to run up to said pick-up device in the press section for the transfer of the formed paper web to said felt. Background Art Conventional soft crepe paper machines of the above kind are widely known, see U.S. Patent No. 4,055,461, for example. The soft crepe paper manufactured in such machines has certain limited values for bulk and softness. To achieve bulk and/or softness values above these limited values, special methods have been utilized, such as mixing in expandable microspheres of thermoplastics as disclosed in U.S. patent No. 4,619,734, or utilizing machines operating with through-air drying by means of hot air, see U.S. Patent Nos. 3,303,576, 3,812,000, 3,821,068 and 4,036,684, for example, where the through-air drying is carried out on cylinders having a perforated shell, which may be covered by a fabric, for exam¬ ple, and where hot drying air is supplied internally and passes out through the shell or the reverse. However, the known conventional soft crepe paper machines of twin wire, fourdrinier, or breast roll former type are designed in such a way that they can not readily be converted into different operative designs for making it possible to manufacture soft crepe paper grades of consider¬ ably different requirements for bulk and softness. Disclosure of Invention One object of the present invention is to eliminate the above problem and provide a soft crepe paper machine, which in a simple manner can be converted in order to be adapted to varying situations on the market, such as actual competitive situation and wishes from the consumers. This object is achieved in that the paper machine is designed to be simp¬ le to rebuild between said first operative design and a second operative design for the manufacture of soft crepe paper having higher measurements of bulk and softness in relation to the first operative design, in which second operative design a conveying and imprinting fabric loop is substi¬ tuted for the felt of the press section, air current generating means being provided along at least one of said fabrics for the removal of water from the paper web by flow of air of ambient temperature through the paper web carried by the fabric in question, cleaning means being provided along the conveying and imprinting fabric for the cleaning thereof so as to continuously maintain its permeability to water and air, and means being provided for depleting the conveying and imprinting fabric of water before the arrival thereof at said pick-up device. Another object of the invention is to eliminate the above problem and provide a paper machine for the manufacture of a soft crepe paper grade, which in respect of bulk and softness is comparable to the one manufac¬ tured on a machine made for through-air drying by hot air. This object is achieved in that the paper machine is provided with (a) a wire section including at least one forming fabric for forming a soft crepe paper web; (b) a drying section including a Yankee dryer for drying the web; (c) a press section located between the wire section and the drying sec- tion and including a conveying and imprinting fabric for conveying the web from the forming fabric to the Yankee dryer and a press roll for pressing the web on to the Yankee dryer while imprinting the web; (d) a pick-up device for picking up the web from the forming fabric and transferring the web to the conveying and imprinting fabric without any appreciable compaction of the web; (e) means for cleaning the conveying and imprinting fabric; (f) means for depleting the conveying and imprinting fabric of water before the arrival thereof at said pick-up device; and (g) air current generating means for removing water from the paper web by running a flow of air of ambient temperature through the paper web, said air current generating means having a capacity that is sufficient for raising the dry solids content of the paper web to at least 25% be¬ fore the arrival of the paper web at the Yankee dryer. Brief Description of the Drawings The invention will below be explained more in detail with reference to the drawings, where Fig. 1 schematically shows a preferred embodiment of a paper machine according to the invention for the manufacture of soft crepe paper. Fig.2 schematically shows a section of the paper machine according to Fig.l equipped with a single-felted press co-operating with a press roll located at the Yankee dryer. Fig.3 is a diagram illustrating the interrelation between density and basis weight of soft crepe paper manufactured in machines of two differ¬ ent operative designs. Modes for Carrying Out the Invention With reference to figure 1 there is schematically shown parts of a con¬ ventional paper machine suited for the manufacture of soft crepe paper, such as tissue and other sanitary paper products. The shown paper ma¬ chine is a twin-wire machine including a wire section 1, a press sec¬ tion 3 and a drying section 5. Wire section 1 has a headbox 7, an end¬ less carrying or inner forming fabric loop 9, an endless covering or outer forming fabric loop 11, and a forming roll 13 that may have a per- forated surface and be equipped with internal suction apparatus or, al¬ ternatively, have a plain surface. Headbox 7 discharges a single layer or a multi-layer stock jet into a gap between the two moving forming fabrics 9, 11 for the forming of a paper web 15 by the drainage of water from the stock. The two forming fabrics run together over the forming roll 13 and then in individual loops over a plurality of rolls, which are arranged to guide, align and tension the carrying or inner forming fabric 9 and the covering or outer forming fabric, respectively. The rolls for the covering forming fabric 11 include a breast roll 17 and a guide roll 19, which is located a short distance downstream of the form¬ ing roll 13 and may be called a turning roll. The covering forming fab¬ ric 11 may leave the carrying forming fabric 9 and the paper web 15 ei¬ ther immediately before fabric 9 and paper web 15 run off from forming roll 13 or alternatively, when required or preferred, at a transfer suc¬ tion box 21 or some other transferring device, which preferably operates by air flow, located between forming roll 13 and turning roll 19. The carrying forming fabric 9 runs up to press section 3, where the paper web 15 is transferred to press section 3 by means of a pick-up device 23 included in the press section. Press section 3 has an endless looped movable fabric 25, which in a first operative design of the paper machine is a felt, that is a fabric provided with a fine fiber surface ("nap") of a natural or synthetic material. The felt is arranged to convey paper web 15 from pick-up de¬ vice 23 to a nip formed between a press roll 27 and a Yankee dryer 29 incorporated in the press section 5. Press roll 27 presses paper web 15 on to the jacket surface of Yankee dryer 29 simultaneously as felt 25 and press roll 27, which in this operative design of the machine prefer- ably is a roll having a perforated surface, remove moisture from the paper web. After said nip felt 25 extends around a guide roll 31 and up to and through a second nip formed between a second press roll 33 and Yankee dryer 29, where felt 25 once more is pressed against paper web 15 to effect removal of any pattern caused by the perforated surface of the first press roll 27. Downstream of second press roll 33 there are means for cleaning and conditioning felt 25, which after the conditioning thereof should have a moisture content suited for the picking up of paper web 15 from carrying forming fabric 9. Yankee dryer 29 is covered by a hood, not shown, in which hot air of high velocity is ejected against paper web 15. The paper web is creped off from Yankee dryer 29 by means of a creping doctor, not shown, in order to obtain a desired creping degree, whereupon the finished creped paper web is wound in a reel-up (not shown). The second operative design of the paper machine is intended for the - manufacture of a soft crepe paper having higher values of bulk and soft¬ ness than what is obtainable in the paper machine according to the first operative design. To achieve this we substitute a conveying and imprint¬ ing fabric for felt 25. The use of imprinting fabrics in the manufacture of soft crepe paper, their functioning and the advantages achieved there- 10 by are well known, cf. Pulp & Paper, November 1977, Hanson, J.P., "What's going on in tissue?", pages 93-102, especially pages 98 - 100 (Never underestimate knuckle power), for example. Further, we provide air current generating means 35, 37 and 39 along at least one of carrying or inner forming fabric 9 and conveying and imprinting fabric 15 25 for removing water from paper web 15 by passing air of ambient temperature through the paper web 15 carried by the fabric in question, we provide cleaning means 41, 43 and 45 along conveying and imprinting fabric 25 for the cleaning thereof, so as to continuously maintain its permeability to water and air, and we provide means 47 for depleting 20 conveying and imprinting fabric 25 of water before the fabric arrives at the pick-up device 23. The conveying and imprinting fabric 25 can either run over the same rolls as the felt ran over, or guide roll 31 may be bypassed, so that 25 the conveying and imprinting fabric runs from the first press roll 27, which in the second operative design preferably is roll having a plain surface, along the jacket surface of Yankee dryer 29 directly to the second press roll 33. In both cases it is suitable that the second press roll 33 be taken out of pressing engagement with Yankee dryer 29, so 30 that the paper web 15 will not be exposed to a second imprinting opera¬ tion. The first imprinting operation is effected where the first press roll 27 presses paper web 15 on to Yankee dryer 29, and the pressing on is carried out with a force that preferably is at least 50 kN/m web width. If, however, in the second operative design the first press roll 35 27 is a roll having a perforated surface, e.g. a suction roll, it is suitable to expose the paper web 15 to a second imprinting operation by means of the second press roll 33 in order to remove the pattern that may be caused by the perforations of the first press roll 27. For the paper machine in the second operative design to operate in the intended manner and produce a marketable soft crepe paper grade it is of utmost importance to maintain conveying and imprinting fabric 25 clean and, in addition, depleted of water upon its arrival at pick-up device 23. Because thereof, the cleaning equipment 41, 43, 45 is more extensive than what is required for cleaning and conditioning a felt in a conven¬ tional soft crepe paper machine and comprises a plurality of oscillating needle jet shower pipes 41, a plurality of fish-tail jet shower pipes 43 and a plurality of suction boxes 45. After installation of these shower pipes and suction boxes, they may, of course, be used also for the clean¬ ing and conditioning of a felt, but then you do not normally use all of the shower pipes and the suction boxes. Two of the fish-tail jet shower pipes 43 are shown located and directed so as to produce a flooded nip where fabric 25 starts wrapping a guide roll. A flooded nip is particu- larly suitable for the cleaning and conditioning of a felt but is useful also for the cleaning of conveying and imprinting fabric 25. A conditioned felt shall contain such an amount of water that the pick¬ ing up of paper web 15 from forming fabric 9 is facilitated. In contrast hereto the conveying and imprinting fabric 25 is to be depleted of water by a water depleting means 47 upstream of the pick-up location. The wa¬ ter depleting means 47 suitably operates by means of an air flow passing through the conveying and imprinting fabric, and in the shown embodiment it is a suction box 47 but it would, of course, be possible to use alter- natively a blow nozzle solely or in combination with the suction box. Suction box 47 and at least one of suction boxes 43 may suitably be moun¬ ted so as to make them easily movable between an active position, in which they engage fabric 25, and an inactive position, in which they do not, since they do not have to be active when fabric 25 is a felt. A plurality of shower water save-alls 49 are provided for collecting the shower water passing through fabric 25 without being sucked into the cleansing suction boxes 45. In a conventional paper machine the pick-up device may be a roll or shoe having a plain surface. For ensuring a picking up without any appreci¬ able compaction of the paper web in the second operative design the pick¬ up device preferably should operate with air flow through forming fabric 9, paper web 15 and conveying and imprinting fabric 25 and it may com- prise a suction device, e.g. a suction roll or, as shown in the preferred embodiment, a suction shoe 51. A still more improved effect is obtained if a blow nozzle 53 is provided inside the loop of the carrying forming fabric 9 and aligned with the suction zone of the shoe 51 or roll. The pick-up device 23 operating with air flow will work excellently also in the first operative design where fabric 25 is a felt. Then, blow nozzle 53 is not required for securing the picking up of paper web 15 from form¬ ing fabric 9. In order to remove in the second operative design at least so much water from the newly formed moist paper web 15 without any appreciable compac¬ tion thereof that when the paper web is pressed on to the hot jacket surface of Yankee dryer 29 no steam bubble formation occurs, which would cause web 15 to come off the jacket surface in places, and also in order to reduce the drying capacity needed, air current generating means are provided for effecting a flow of air of ambient temperature through paper web 15. In the embodiment shown in figure 1 the air current generating means comprise two suction boxes 35, 37 located inside the loop of the carrying forming fabric 9 between transfer suction box 21 and pick-up device 23, and a suction box 39 located inside the loop of conveying and imprinting fabric 25 between pick-up device 23 and first press roll 27. The number of suction boxes 35, 37 and 39 and the location thereof be¬ tween transfer suction box 21 and first press roll 27 may be varied with¬ in the scope of the present invention. However, it is necessary to pay attention to the moist and comparatively fragile soft crepe paper web not adhering to strongly to carrying forming fabric 9 or conveying and imprinting fabric 25. Means 55 may be provided, if desired, for applying a suitable release agent to conveying and imprinting fabric 25 for the purpose of reducing the adherence of web 15 to the fabric. Such means illustratively is a spraying device 55 located on the web facing side of fabric 25 immediately downstream of suction box 47. Conventional means, not shown, are also provided for forming and maintaining at an optimum and stable level a web adherence controlling coating on the jacket sur¬ face of the yankee dryer 29. A natural coating substantially consists of hemicellulose and fiber fragments, but to improve control of the adhesive properties of the coating an adhesive agent and/or a release agent may be added. The amount of hemicellulose is controlled by controlling the pH of the stock, while the chemicals may be added to the stock or applied to the formed paper web or, preferably, directly onto the jacket surface of the yankee dryer. The adhesion of the web to the coating affects all properties of the paper web, and the coating also affects the wear of the yankee dryer surface and of the doctor blade. Some dewatering of paper web 15 also ensues due to the flow of air into transfer suction box 21 and suction shoe 51. In order to improve the dewatering still more a steam box 61 for heating paper web 15 by means of direct steam may be provided immediately upstream of suction box 35 and on the web carrying side of forming fabric 9. The heating reduces the viscosity of the water, so that it will be easier to suck it out. In addition, the dewatering rate will be increased by the sucking through of air. If desired it is, of course, possible to provide in a correspond¬ ing manner a second steam box, not shown, for heating web 15 by direct steam immediately upstream of suction box 39 located inside the loop of the conveying and imprinting fabric 39. In order to shield paper web 15 from condensate drippings and possible splashes of water when carried hanging on the underside of conveying and imprinting fabric 25, a web- covering heatable roof or shield element 63 is placed above the lower run or flight of the conveying and imprinting fabric. Roof element 63 may be provided with conduits, not shown, for conducting hot water or steam therethrough but may also be heated in some other way, e.g. by electricity. In order to avoid the above mentioned formation of steam bubbles between paper web 15 and Yankee dryer 29, the paper web should have a dry solids content of at least about 25 % when the first press roll 27 presses web 15 on to Yankee dryer 29. The number of paper web dewatering suction boxes 35, 37 and 39, the flow of air through web 15, and the possible heating by direct steam are adjusted so as to achieve the aforesaid dry solids content. As a supplement to or a substitute for the heating by direct steam, heating by infrared (IR) radiation may be used, e.g. from one or more hood-type IR heaters, not shown, or other equipment able to emit IR radiation. Hood-type IR heaters may also be used for facilitating the drying of paper web 15 on Yankee dryer 29, and in figure 1 there is shown one such IR hood 65 placed somewhat downstream of second press roll 33. A compact standard hood having a single row of IR elements can emit about 125 kW/m web width. Usually, paper web 15 reaches a dry solids content of about 25-30% al¬ ready on forming fabric 9, and the dry solids content is increased by one or several more percent along conveying and imprinting fabric 25. If it is desired to raise the dry solids content of web 15 still more be- fore the web is pressed on to Yankee dryer 29, it is possible to supple¬ ment the paper machine with a conventional ' single-felted press, as shown schematically in figure 2. In figure 2 the conveying and imprinting fabric 25, which on its under side carries paper web 15, runs from the bottom side of first press roll 27 up to and around a turning roll 67, from where it runs to the press nip formed between first press roll 27 and Yankee dryer 29. Press roll 27 constitutes a counter roll of a conventional single-felted press, generally indicated by 69, having a press roll 71 and an endless felt 73 running over a plurality of rolls 75. A suction box 77 is provided in¬ side the loop of conveying and imprinting fabric 25 upstream of turning roll 67 for securing that paper web 15 will not be transferred to press felt 73 but will remain adhered to conveying and imprinting fabric 25. Such a conventional single-felted press will raise the dry solids con- tent of paper web 15 by up to an additional five percent. In a modification (not shown) of the singlefelted press of Fig. 2, the lower press roll 71 is moved from its illustrated 6 o'clock position in relation to press roll 27 to a 7 o'clock position. This makes it possi- ble to leave out turning roll 67 and suction box 77. After passing from the nip formed between press roll 27, 71, the conveying and imprinting fabric 25, carrying the paper web 15, will then follow the surface of press roll 27 up to the nip formed by roll 27 with yankee dryer 29. From the press nip formed by rolls 27, 71 at the 7 o'clock position the press felt 73 will be run to the 6 o'clock position, and then will pass tangen- tially and horizontally from roll 27. Consequently, paper web 15 will not be transferred to the press felt 73, but will instead remain adhered to the bottom side of conveying and imprinting fabric 25 when the latter passes upwardly on press roll 27. In order not to unnecessarily crowd the drawing with details, which mere¬ ly show conventional equipment in paper machines and do not constitute any part of the present invention, such details are omitted. Examples of such non-shown details are cleaning devices for forming fabrics 9 and 11 and for press felt 73, and further, white water save-alls and devices for stretching, aligning and driving the various endless fabrics. Figure 3 is a diagram showing density as a function of basis weight for soft crepe paper manufactured on one hand in a conventional paper ma¬ chine according to the first operative design and on the other hand in the same machine after a rebuilding thereof to the second operative de- sign. A single-felted press in accordance with the variant shown in fig¬ ure 2 was not used. Consequently, the upper line 79 relates to a soft crepe paper manufactured in the conventional manner, and the lower line 81 relates to soft crepe paper manufactured in the rebuilt machine, where the conveying and imprinting fabric was substituted for the pick- up felt, and where water was removed from the paper web by passing air of ambient temperature through the web in an amount sufficient for rais¬ ing the dry solids content of the paper web to at least about 25% before the paper web arrived at the Yankee dryer. As is apparent from the dia¬ gram, the latter soft crepe paper 81 has a density, which at low basis weights is about half the density of the conventional soft crepe paper, and the percentage difference increases with increasing basis,weight. 3 Since bulk is inverted density, a density of 200 kg/m , for example, 3 3 corresponds to a bulk of 5 dm /kg, and a density of 80 kg/m corresponds 3 to a bulk of 12.5 dm /kg, the soft crepe paper in accordance with line 81 has at low basis weights twice as high a bulk as conventional soft crepe paper and the percentage difference in bulk increases with in¬ creasing basis weight. The density of soft crepe paper manufactured in a conventional through- air drying machine using hot air is essentially of the same order as that indicated by the lower line 81. The bulk of a soft crepe paper grade in accordance with the lower line 81 consequently is fully comparable to the one manufactured in a through-air drying machine utilizing hot air. While the softness has not been measured, it is well known that the soft- ness increases with increasing bulk of the soft crepe paper. The in¬ creased softness is appreciated by consumers but in some cases can result in adaptation problems during conversion of the soft crepe paper web to the desired end products. The rebuilding required for converting the paper machine according to the invention from one operative design into the other essentially con¬ sists of a change from pick-up felt into conveying and imprinting fabric or the reverse. What is additionally required is that certain components, e.g. second press roll 33, water depleting suction box 47 and possibly one of the suction boxes 45 of the cleaning means for conveying and im¬ printing fabric 25, are changed from an inactive to an active position, and that other components, such as one or more of shower pipes 41, 43 and the possible device 55 for applying a release agent on to the convey- ing and imprinting fabric, are activated or inactivated. In addition it is preferred, but not absolutely required, in cases where the first press roll has a perforated surface, to substitute for said roll a roll having a plain surface. The time required for the rebuilding will as a conse¬ quence, be short. The rebuilding should be finished in only a slightly longer time (about 12 hours or less) as is needed for changing the pick¬ up felt in a conventional soft crepe paper machine. The cost of converting an existing old soft crepe paper machine into paper machine according to the present invention is estimated to be 10-20% of the price of a new through-air drying machine. Thus, for a comparatively low machine cost a soft crepe paper manufacturer can produce a soft crepe paper grade, which with regard to bulk and softness is fully comparable to the one manufactured in a machine using through- air drying by hot air. Roughly, the production will be halved, since a large part of the dewatering is carried out by through-flow of air of ambient temperature followed by drying on the Yankee dryer, which re¬ quires a considerably lower machine speed, about half of that of a con¬ ventional soft crepe paper machine, but production costs for the pro¬ duced high bulk soft crepe paper will be of the same order as with pro- duction in a through-air drying machine. A look at the costs of the end- product sold to the consumer, e.g. a package of paper handkerchiefs, shows that the change-over from conventional handkerchief paper to high bulk handkerchief paper produced in the paper machine according to the invention gives the possibility of such savings in the amount of paper fibres used, that the cost for the finished product can be reduced. In addition, the consumer will get a softer and more attractive product. The fact that it is possible to produce in a conventional soft crepe paper machine a soft crepe paper without having to use a pick-up felt must be characterized as unexpected. In addition it was unexpected that the soft crepe paper grade produced in the machine according to the in- vention should be fully comparable, in respect of bulk and softness, to the one produced in a paper machine made for through-air drying by hot air. The invention has been described above with reference to a twin-wire former of C-wrap type but, of course, it can be applied also in other formers, e.g. twin-wire formers of S-wrap type, fourdrinier formers and suction breast roll formers.

Claims: CLAIMS 1. A paper machine for the manufacture of soft crepe paper and including a wire section (1), which has at least one forming fabric loop (9) for forming a paper web (15), and a drying section (5) including a Yankee dryer (29), in which drying section the paper web (15) is dried, said paper machine having a first operative design for the manufacture of soft crepe paper having certain measurements of bulk and softness, in which first operative design a press section (3) located between the wire section (1) and the drying section (5) has a felt (25) movable in an endless loop and arranged to run from a pick-up device (23) located at a transition between the wire section (1) and the press section (3) to a press roll (27) forming a nip with the Yankee dryer (29) while car¬ rying the paper web (15) on its underside, the carrying forming fabric (9) being arranged to run up to said pick-up device (23) in the press section (3) for the transfer of the formed paper web (15) to said felt (25), characterized in that the paper machine is designed to be simple to rebuild between said first operative design and a second operative design for the manufacture of soft crepe paper having higher measure- ments of bulk and softness in relation to the first operative design, in which second operative design a conveying and imprinting fabric loop (25) is substituted for the felt (25) of the press section (3), air cur¬ rent generating means (35,37,39) being provided along at least one of said fabrics (9,25) for the removal of water from the paper web (15) by flow of air of ambient temperature through the paper web (15) carried by the fabric in question, cleaning means (41,43,45) being provided along the conveying and imprinting fabric (25) for the cleaning thereof so as to continuously maintain its permeability to water and air, and means (47) being provided for depleting the conveying and imprinting fabric (25) of water before the arrival thereof at said pick-up device (23). 2. A paper machine according to claim 1, wherein in the first operative design there is provided a second press roll (33), which downstream of the first mentioned press roll (27) forms a second nip with the Yankee dryer (29), and wherein the felt after the first mentioned nip runs over a guide roll (31) to and through the second nip, where it is pressed against the paper web (15), characterized in that in the second operat¬ ive design the second press roll (33), in case the first press roll (27) has a plain surface, is lifted out of pressing contact with the Yankee dryer (29), so that a second imprinting of the paper web (15) is avoid¬ ed. 3. A paper machine for the manufacture of a soft crepe paper grade, which in respect of bulk and softness is comparable to a grade manufactured on a machine made for through-air drying by hot air, characterized by (a) a wire section (1) including at least one forming fabric (9) for forming a soft crepe paper web (15); (b) a drying section (5) including a Yankee dryer (29) for drying the web (15); (c) a press section (3) located between the wire section (1) and the drying section (5) and including a conveying and imprinting fabric (25) for conveying the web (15) from the forming fabric (9) to the Yankee dryer (29) and a press roll (27) for pressing the web (15) on to the Yankee dryer (29) while imprinting the web (15); (d) a pick-up device for picking up the web (15) from the forming fabric (9) and transferring the web (15) to the conveying and imprinting fabric (25) without any appreciable compaction of the web (15); (e) means (41,43,45) for cleaning the conveying and imprinting fabric (25); (f) means (47) for depleting the conveying and imprinting fabric (25) of water before the arrival thereof at said pick-up device (23); and (g) air current generating means (35,37,39) for removing water from the paper web (15) by running a flow of air of ambient temperature through the paper web (15), said air current generating means (35,37,39) having a capacity that is sufficient for raising the dry solids content of the paper web to at least 25% before the arrival of the paper web (15) at the Yankee dryer (29). 4. A paper machine according to any one of clamis 1-3, characterized by said pick-up device (23) picking up said web (15) pneumatically. 5. A paper machine according to clamim 4, characterized by said pick-up device (23) including a suction member (51) located inside the conveying and imprinting fabric loop (25) for picking up the paper web (15) from the forming fabric and transferring the web (15) to the conveying and imprinting fabric (25) without appreciably compacting the web (15). 6. A paper machine according to claim 5, characterized by said pick-up device (23) including a blow nozzle (53) located inside the forming fab¬ ric loop (9) and aligned with a suction opening provided in the suction member (51). 7. A paper machine according to any one of claims 1-6, characterized by said air current generating means including at least one suction box (35,37,39). 8. A paper machine according to claim 7, characterized by a steam box (61) for heating the moist paper web (15) by means of direct steam and located immediately upstream of the suction box (35) and on the web car¬ rying side of the fabric (9). 9. A paper machine according to any one of the preceding claims, charac¬ terized by at least one hood-type IR heater (65) for IR heating of the paper web (15). 10. A paper machine according to claim 9, characterized by said IR hood (65) being located at the Yankee dryer (29) downstream of the press roll (27). 11. A paper machine according to any one of claims 1-10, characterized by said press roll (27) constituting a counter roll in a single felted press (69) for additional dewatering of the web (15) before the press roll (27) presses the web (15) on to the Yankee dryer (29; Fig. 2) 12. A paper machine according to any one of claims 1-11, characterized by a heatable roof element (63) located above the lower run of the con- veying and imprinting fabric (25) for protecting the paper web against splashes of water and condensate drippings. 13. A paper machine according to any one of clamis 1-12, characterized by means (55) for applying a web adherence reducing release agent to the conveying and imprinting fabric (25).

Inventors: ERIKSON JAN ANDERS, LINDEN ANDERS TOMMY, ERIKSON, JAN, ANDERS, LINDEN, ANDERS, TOMMY
Applicants: VALMET KARLSTAD AB, VALMET-KARLSTAD AB
Application year: 1991
Main classification: D21F9
IPC codes: D21F1, D21F9, D21F11, D21H27