Source: http://www.google.com/patents/US5092962?dq=6011510
Timestamp: 2017-10-23 21:20:34
Document Index: 172808838

Matched Legal Cases: ['art 68', 'art 62', 'art 62', 'art 68', 'art 68', 'art 68', 'arts 68', 'art 68']

Patent US5092962 - Hot-pressing and drying device - Google Patents
A device is provided for the removal of water from a web by hot-pressing while the web is in direct contact with a heated cylinder face. The web is passed, while being supported by a press fabric, through at least two separate press stages. The web is first passed into direct contact with the heated...http://www.google.com/patents/US5092962?utm_source=gb-gplus-sharePatent US5092962 - Hot-pressing and drying device
Publication number US5092962 A
Application number US 07/495,484
Also published as CA2012726A1, CA2012726C, US5164047
Publication number 07495484, 495484, US 5092962 A, US 5092962A, US-A-5092962, US5092962 A, US5092962A
Inventors Erkki Koski
Patent Citations (17), Referenced by (42), Classifications (16), Legal Events (6)
Hot-pressing and drying device
US 5092962 A
A device is provided for the removal of water from a web by hot-pressing while the web is in direct contact with a heated cylinder face. The web is passed, while being supported by a press fabric, through at least two separate press stages. The web is first passed into direct contact with the heated cylinder face and into an extended-nip press stage. At the beginning of the extended-nip press stage, a press-glide belt is passed into contact with the press fabric. The press-glide belt is pressed by means of a press member in the extended-nip stage against the heated cylinder face. This press-glide belt is separated from the fabric and the web is passed to the next stage where the web is pressed against a cylinder face only by means of the tension of the press fabric. After this latter stage, the web is passed to an intensive roll-nip pressing stage, through a roll-nip which is formed between the hot cylinder and a hollow-faced press roll. In this stage, water is removed from the web into the press fabric and into the hollow face of the press roll. The press fabric is separated from the web, which is then detached from the face of the hot cylinder.
1. Hot pressing device for the removal of water from a paper or board web by hot-pressing which takes place when the web is in direct contact with a heated roll or cylinder and in which the web is to be pressed is passed, supported by a press fabric, through at least two separate press stages, said device comprising:
a hot cylinder or roll provided with a smooth outer face,
heating means for heating the smooth outer face of said hot cylinder or roll,
said press fabric guided by rolls and press members which form press zones together with the hot cylinder and through which press zones said web to be pressed, supported by the fabric, are passed into direct contact with the heated face of the hot cylinder or roll,
a belt roll provided with a hose-like, press-glide belt mantle, having at least one press member located inside said mantle, forming a pressure-loaded extended nip against the hot cylinder,
said belt roll and press glide belt mantle being arranged in such manner that said press glide belt mantle enters into contact with the fabric substantially at the beginning of the extended nip and departs from the fabric at the end of the extended nip or slightly thereafter, and before an intensive roll-nip pressing stage, and
a hollow faced press roll arranged to form the intensive roll-nip pressing stage with said fabric, web, and hot cylinder, and a guide roll for separating the web from the face of the hot cylinder or roll after the press zones.
2. Device according to claim 1, wherein the hot pressing device is preceded by a closed press section.
3. Device according to claim 1, wherein the belt roll forming the extended nip comprises a stationary central axle and wherein both ends of the mantle of the belt roll are sealed by sealing arrangements preventing splashing of fluid.
4. Device according to claim 1, and including a transfer-suction roll before the hot cylinder over which the press fabric is passed, the web being arranged to be transferred onto the press fabric in a suction zone of said transfer-suction roll, the press fabric and the web supported on the upper face of said press fabric being passed into direct contact with the heated face of the hot cylinder or roll.
With increasing production rates of paper machines, the dewatering performed as nip pressing has become a bottleneck that limits the increase in the running speeds, because the press nips formed by a pair of rolls have a short area, so that with high speeds, the time or dwell of the web in these press nips remains short.
Attempts can be made to extend the compression area in roll-nips by using rolls of larger diameter and soft press fabrics. However, even with these means, the limit of an economically satisfactory embodiment is soon reached. As a result of these problems, and for other reasons, so-called extended-nip presses have been invented in recent years. Reference may be made in this respect by way of example to U.S. Pat. Nos. 3,783,097; 3,808,092; 3,840,429; 3,970,515; 4,201,624; and 4,229,253, as well as Finnish Patents to Nos. 65,104; 70,952; and 71,369.
Extended-nip presses are known in the prior art wherein the press area is formed between a revolving hose mantle, provided with a stationary core and a counter-roll. In the stationary roll core, hydraulically loaded pressure shoes are utilized by means of which, with the intermediate of the revolving mantle, a compression pressure is applied to the web towards the counter-roll. The counter-roll may be either an ordinary press roll or a roll provided with a hydraulic glide shoe. As examples of the prior art extended-nip press of the type described above, reference is made to British Patent Application No., 2,057,027, to be published as Patent Application WO 82/02567, and to Finnish Patent No. 66,932. So called hot-pressing methods are also known in the prior art, and reference is made by way of example to U.S. Pat. No. 4,324,613, and to U.S. patent application Ser. No. 07/187,259 filed on Apr. 22, 1988, now U.S. Pat. No. 4,976,820.
The sharp second nip employed in accordance with the present invention is an ordinary roll-nip, wherein a grooved roll or some other hollow-faced roll is used. The linear load in this nip is most preferably on the order of 150 kN/m, or, if necessary, greater. Comparing the present invention with the hot-pressing methods and devices described in the Finnish Patent Applications 871871 and 880700, it is noticed that in the second nip, the dewatering takes place by means of conventional roll pressing technique, and in accordance with the invention, no particular grooved belt is needed because the dewatering space can be arranged in the conventional hollow-faced press roll. In the invention, in the area between the nips, the felt tensioning pressure P=T/R (R is the radius of the hot cylinder, T is felt tension), presses the paper web with a low force against the hot cylinder. The length of and the compression pressure in the zone are not at all critical in connection with the present invention.
As is shown in FIG. 1, the board or paper web Win, whose dry solids content, as a rule, within the range of 20-45%, is introduced over the paper guide roll 52, onto the press felt 12, to which it is made to adhere by means of the negative pressure of the suction zone 22a, of the suction roll 22. The web W is then passed into the extended-nip Np which has a relatively wide press zone A (FIG. 2). The extended nip Np is formed between the hot cylinder 10 and the belt roll 30, which is provided with a flexible mantle 35, and which acts as the lower roll in the extended nip Np. In the extended nip Np, heating of the web W takes place to about 902°-100° C., but vaporization of water does not necessarily take place. It is for this reason that the temperature of the hot cylinder 10 does not have to exceed about 90°-150° C., i.e. approximately the same as with the prior art drying cylinders. The primary aim of the load in the extended nip Np, is to improve heat transfer and not so much dewatering of the web W.
As shown in FIG. 2, the compression pressure P1, used in the extended nip Np, is most appropriately about 0.5-1.5 MPa. After the extended nip Np, the web W enters sector B, the length of which is, for example, about 500-700 mm (in FIG. 2, B=600 mm). In the zone B, a compression pressure Po =T/R (R is the radius of cylinder 10) prevails, which is based on the tension T of the press felt 12 and wherein the compression pressure Po is on the order of approximately 5 kPa.
After the zone B, between the rolls 30 and 20, the web W is passed into the roll-nip N, which is formed between the hot cylinder 10 and an ordinary press roll 20 provided with a hollow face 20'. In a manner per se known, the hollow face 20' may be a grooved face, a blind-drilled face or the equivalent. The press roll 20 is preferably provided with a drive 20a and if necessary, it may also be a variable-crown or adjustable-crown roll. In the press nip N, the hollow face 20' acts as a space that receives water, together with the structure of the felt 12. The roll-nip N is quite sharp, and the length C of this zone, is a rule, with the range of C=30-50 mm. In FIG. 2, zone C=35 mm. The maximum compression pressure Pmax prevailing in the nip N is on the order of 6-7 MPa (in FIG. 2, Pmax =6.5 MPa), which corresponds to a range of linear load of 135-155 kN/m.
After the nip N, the web W separates from the press felt 12, which is guided from by the guide roll 19 and which is passed to reconditioning. Thereupon, the web W follows the smooth face 10 of the cylinder 10, from which it is detached as the draw Wp, by means of a guide roll 13 provided with a drive 13a, transferred onto the support of the drying fabric 15, guided by the guide roll 14, aided by section, where the removal of water is continued by evaporation.
It is an important feature of the invention that in the formulation of the extended nip Np, a particular belt roll 30 is used which is provided with a flexible belt mantle 35. The hose roll 30 is provided with a stationary roll core 32, or with an equivalent frame beam. The roll core 32 is supported on supports 56 by means of its axial journals 55 (FIG. 3), and by the intermediate of a ring 57 which has a spherical face. The supports 56 are attached to the frame parts or foundations of the press by the intermediate of trestles or the equivalent. A thin walled mantle 35, which is pressed from inside by a hydraulically loaded shoe 31, in the area of the extended press zone A formed with the cylinder 20, revolves around the stationary core 32.
The roll core 32 comprises a number of radial grooves in which there are ribs 34 loaded by springs 33. Glide shoes 36 are supported on the ribs 34 by the intermediate of bearing rolls, the glide shoes 36 gliding and supporting the revolving mantle 35. The glide shoes 36 and the press shoe 31 require lubrication, and for this purpose lubricant is fed from several different points, (not shown) onto the inner face of the mantle face 35, and/or onto the glide faces of the glide shoes 36 and of the press shoe 31. The press shoe 31 is loaded by a number of hydraulic cylinders placed side by side, or by a corresponding rib-like piston or pistons by the intermediate of a bearing roll or rolls. The rib-like piston or pistons, is/are loaded by means of hydraulic fluid which is introduced through ducts into the roll core 32 from sources of pressure medium (not shown) which in themselves are known. By means of regulation of the pressure of the pressure fluid, it is possible to alter the compression pressure in the extended nip Np.
As is seen from FIG. 1, the roll mantle 35 must change its shape considerably from the circular shape in the area of the press shoe 31, and of the press zone A. It is not necessary that the roll mantle 35 be expressly of circular shape when guided by the shoes 36 outside the area of the press zone A. In some cases, an elliptical form, a crawler form, or a continuous "heart-shaped" form of the mantle 35 may be preferred. The construction of the ends of the mantle 35 permits the use of a cross sectional form of the mantle 35 which can vary within very wide limits.
As shown in FIG. 3, a bushing part 68 is mounted by means of bearings 67a and 67b around each axial journal 35 of the roll core 32. The outer end of the bushing part is provided with a cogwheel 64 provided with a toothed rim 65. The cogwheel 64 is driven by a cogwheel 60, which is mounted at the end of a shaft 58 and which is provided with a toothed rim 61. The shaft 58 is mounted on bearings 69a and 69b, placed at a distance from one another. These bearings are fitted in part 62, which is supported to be stationary on the supports 56 of the axial journals 55. Between the part 62 and the revolving part 68, there is sealed grooved-projection fitting 63 which permits rotation.
An elastic seal ring 70 is fixed by the intermediate of its edge flange 70', between the fastening ring 69 and the projection part 68' of the revolving part 68. The edge of the flange 70' is attached into the groove between the parts 68' and 69 by means of a screw fastening 71. In the interior 72 of the elastic seal ring 70, by means of a valve (not shown), an appropriate air pressure is arranged which presses the seal ring 70 against the inner face of the mantle 35. The shaft 58 rotates the seal ring 70 by the intermediate of the part 68 synchronously with the operation of the roll 10.
Owing to its elasticity, the seal ring 70 permits deformations of the mantle 35 during each revolution such that, in spite of these deformations, the sealing remains adequate and fluid cannot enter out of the space 53 between the mantle 35 and the roll core 32, into places to which it should not have access. By regulation of the pressure in the interior 72 of the seal ring 70, it is possible to appropriately vary the elasticity of the seal ring 70. The outer parts of the seal ring 70 are preferably made, e.g. of rubber without reinforcements, whereas in the inner parts of the ring 70, and in the fastening flange 71, it is possible to use reinforcement fabrics, if necessary such fabrics being impregnated, for example, into the rubber material. The sealed ring 70 resembles, for example, the air-tight tubes of vehicle tires, with the exception of the fastening flange 70.
In this connection, it should be emphasized that the above description with reference to FIG. 3, exemplifies only one embodiment of a hose roll. However, it is possible within the scope of the invention to use several different hose roll constructions, e.g. constructions that are described in Finnish Patent No. 66,932, or in U.S. patent application Ser. No. 486,754, filed Mar. 1, 1990, now U.S. Pat. No. 5,043,046. For the purposes of the present invention, it is an important feature of the construction of the hose roll that, in one way or another, splashes of lubricant necessary for lubrication of the pressure 31 and the glide belt 35 and the possible other guide members 34 in the hose roll onto the press belt 12 and to the web W are prevented.
FIG. 4 illustrates an advantageous mode of application of the invention in combination with the SYM-PRESS II (Trademark) press section SP. The web W is formed on the forming wire 40, transferred onto the felt 41, at the suction zone 41a of the pick-up roll. The web W is transferred further, supported by the felt 41, through the first nip N1 in the closed press section SP, said nip being formed by the press roll 43 and the suction roll 44. The lower press felt 42 runs through the nip N1. In order that the dry solids content and the temperature of the paper web W be as high as possible before the hot pressing devices, it is advantageous to use preheaters for the web W. As shown in FIG. 4, such device may be the heater 49 operating against the suction sector 44a of the suction roll 44, such heater being, e.g., a steam box, an infrared heater, or a high frequency heater. The second nip N2 in the press section SP is formed between the suction roll 44 and the smooth-faced center roll 45. The web W adheres to the smooth face 45' of the center roll 45, and is transferred onto it and into the third nip N3 in the press section SP, which is formed between the center roll 45 and the hollow fased roll 46. The press felt 47 runs through the third nip N3.
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U.S. Classification 162/358.5, 162/206, 100/332, 162/360.3
Cooperative Classification D21F3/0218, D21F3/045, D21F3/04, D21F3/0245, D21F3/0281
European Classification D21F3/04, D21F3/02D, D21F3/02B2B2, D21F3/04B, D21F3/02B2
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:KOSKI, ERKKI;REEL/FRAME:005266/0154