|Publication number||US3257268 A|
|Publication date||21 Jun 1966|
|Filing date||13 Feb 1962|
|Priority date||13 Feb 1962|
|Also published as||DE1411905A1|
|Publication number||US 3257268 A, US 3257268A, US-A-3257268, US3257268 A, US3257268A|
|Inventors||Peter E Wrist, Christian A Schiel|
|Original Assignee||Mead Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (7), Classifications (16)|
|External Links: USPTO, USPTO Assignment, Espacenet|
;June 21, 1966 P. E. WRIST ETAL 3,257,268 PAPER PRESSING PROCESS AND APPARATUS UTILIZING WATER RECEIVING BELT Filed Feb. 13, 1962 5 Sheets-Sheet 1 TER E WNVENTORS PE v CHRISTIAN A. HIEL 2 m il ATTORNEY June 21, 1966 p. wms-r ET 3,257,268
NG P NG PAPER PRESSI ROCESS AND APP TUS UTILIZI WATER RECEIVING BELT Filed Feb. 13, 1962 5 Sheets-Sheet 2 INVENTORS. PETER EWRIS CHRISTIAN A. S EL kw- M ATTORNEY June 21, 1966 P. E. wms-r ETAL 3,257,263
PAPER PRESSING PROCESS AND APPARATUS UTILIZING ECEIVIN WATER R G BELT Filed Feb. 13, 1962 5 Sheets-Sheet 5 INVENTORS, PETER E. WRI
CHRISTIAN A. IEL BY ATTORNEY June 21, 1966 w s-r ETAL 3,257,268
PAPER PRESSING PROCESS AND APPARATUS UTILIZING WATER RECEIVING BELT Filed Feb. 13, 1962 5 Sheets-Sheet 4 m QE INVENTORS. PETER E.WR|ST CHRISTIAN ASCHIEL BY g ATTORNEY June 21, 1966 P. E. WRIST ETAL 3,257,268
ING PROC ZING ESS AND APPARATUS UTILI WATER RECEIVING BELT Filed Feb. 13, 1962 5 Sheets-Sheet 5 PAPER PRESS INVENTORS PETER E. WRIST CHRISTIAN A. SCHIEL BY ATTORNEY United States Patent 3,257,268 PAPER PRESSING PROCESS AND APPARATUS UTILIZING WATER RECEIVING BELT Peter E. Wrist and Christian A. Schiel, Chillicothe, Ohio,
assignors to The Mead Corporation, Dayton, Ohio, a
corporation of Ohio Filed Feb. 13, 1962, Ser. No. 173,005
5 Claims. (Cl. 162-199) This invention relates to improved methods and apparatus for drying moving Webs. More particularly, the methods and apparatus of this invention remove entrained liquids from moving Webs containing the same.
The invention finds particular application .to the removal of water from moving webs of paper, pulp, paperboard or the like. In the manufacture of such webs, the newly formed fibrous web, still containing considerable water, is generally carried by a supporting felt through a series of presssing stations which are generally cooperating rollers acting much like wringer rolls to squeeze water from the web. With solid rollers, the expelled water passes through the supporting felt onto the upward turning surface of the bottom press roller, from which it drains by gravity to trays of one kind or another. Alternatively, one or both such press rollers may he hollow and provided with a perforated shell and a suction chamber which acts in the nip area, such presses generally being called vacuum presses to distinguish them from presses utilizing solid rolls, and which are generally known as plain presses. In vacuum presses, water expressed from the web is drawn through the felt and passes into the perforated shell. On passing beyond the pressure nip, this water is either sucked into the suction chamber or else thrown outward into collecting pans.
Vacuum presses have increased water removal capacity as compared to conventional plain presses, especially at high speeds, for example, speeds in excess of 800 feet per minute. However, they also have important limitations and disadvantages. At high speeds, massive vacuum systems are required to handle the large volumes of air and water passing through the suction rolls. The perforations around the suction roll shell, cooperating with the internal suction chamber, can generate objectional high volume noise. Further, water in the perforations, moving past the suction chamber, is thrown out radially by centrifugal force and unless deflected by cumbersome shields, it can rewet the felt and the partially dried web. Such suction presses have a high capital cost and re quire considerable maintenance. Effective water removal by vacuum presses at high speeds requires higher nip loading to compensate for the short time the web is subjected to pressure in the nip land. To handle such high nip pressures with rolls having perforated shells, increasingly large roll diameters are required. Hence, cost and space limitations place a practical limit on the nip loading which can be used in vacuum presses. On some of the higher quality paper grades, a further nip pressure limit is imposed by the occurrence of so-called shadow marking of the web which is aggravated by high nip pressures On the other hand, water expelled from the web by a plain press must move out of the nip region against the direction of travel of the felt and web, then flow down the up-turning face of the lower press roll under the influence of gravity and counter to the direction of travel of the roll surface. At high speeds, higher nip pressures are required to force the water out of the nip against the direction of felt travel. Soon a threshold is reached where the increased water content of the felt in combination with the increased pressure gradient at the ingoing part of the nip will disrupt or crush the web structure, thus causing substantially complete process failure.
A prior approach seeking to improve operation of such plain presses traps expelled water in a mat or belt which passes through the press nip between the roll surface and the felt. This mat is provided with openings, and in operation, water expelled from the web passes through the felt and enters the openings in the mat. After leaving the nip region, the web and felt are separated from the mat, and at a point remote from the press rolls, the mat is caused to make a sudden change in direction of travel, whereupon the water in the openings is thrown out of the mat by centrifugal force. However, the centrifugal action leaves some water in the mate, which must be removed therefrom by other means, such as suction, heat or pressure.
The present invention for more efliciently drying moving webs generally comprises the utilization of a waterreceiving woven fabric interposed, in the nip region, between a press roll surface and the conventional press felt. And as used herein, the term fabric refers to an openpored structure which is not felted or fulled, and is relatively incompressible; while the term felt has the usual meaning associated with papermaking, -i.e., a finely woven structure which has been fulled or felted, and is relatively compressible. The fabric is in the form of a continuous loop of material which follows a path generally inside the path followed by the press felt, the fabric and felt traveling together through the nip of the press rolls. The wet web is supported on the opposite side of the press felt, so that the latter is sandwiched between the web and the fabric in the nip region. In this arrangement, water expelled from the web by the action of the press rolls travels through the felt and is received in the interstices of the fabric. These interstices act as small cells which carry the water through the nip, rather than requiring such water to drain from the surface of the press roll on the ingoing side of the nip, as is the prior practice with plain presses. On the outgoing side of the nip, the web, felt, and fabric are separated, the fabric following the surface of the press roll with which it is in contact for at least a short distance. After such travel in contact, the fabric is separated from the roll surface, whereupon water loosely carried in the interstices of the fabric is substantially completely transferred to the roll surface by surface tension forces. In turn, the water on the roll surface is removed therefrom by any convenient means; for example, by a wiping or doctoring element and removed from the system.
Accordingly, it is a principal object of the present invention to provide methods and apparatus to more efficiently and completely remove water from wet webs such as paper, pulp, paperboard and the like.
It is a further object to improve the action of plain wet presses on a paper machine to permit greater water removal from wet webs at high speeds.
Another object is to provide apparatus of low capital cost and low maintenance cost for dewatering wet webs at high speed.
Still another object is to provide methods and apparatus for dewatering wet webs which overcome most of the known disadvantages of the prior art.
The invention will be better understood from the description to follow, the claims defining the invention and from the appended drawings wherein:
FIGURE 1 is a diagrammatic sectional elevation view of one embodiment of apparatus for carrying out the process of the invention;
FIGURE 2 is a magnified diagrammatic sectional view of the nip area of FIGURE 1;
FIGURE 3 is a diagrammatic sectional elevation view of another embodiment of the invention wherein the felt run and fabric run are around the top press roll;
FIGURE 4 is a diagrammatic sectional elevation view of yet another embodiment which provides for additional water removal from the felt and fabric at a point remote from the web;
FIGURE 5 is a diagrammatic sectional elevation view of still another embodiment wherein the teachings of this invention are applied to remove water from -a wet web at two different pressing stations, and from both top and bottom of the web;
FIGURE 6 is a diagrammatic sectional elevation view wherein the novel features of this invention are applied in a multiple pressing arrangement around a central roll; and,
FIGURE 7 is a dragammatic sectional elevation view of the application of this invention to the dewatering of tissue webs. I
' Referring to FIGURE 1, numerals 11 and 12 show two plain press rolls running in contact with bearings and supporting framework not shown. A felt 13 passes around felt idler rolls 14, 15, 16 and 17 to train it in a continuous manner through the nip between press rolls 11 and 12. In addition, a felt stretch roll 18 and guide roll 19 are provided. Running as a continuous band inside felt 13 is a fabric 20 which is trained around fabric idler rollers 21, 22, 23 and 24 to pass it through the nip region in contact with the felt. In addition, stretch roll 25 and guide roll 26 are provided to complete the run of the fabric. Below press roll 12 is a water-collecting.pan 27 and cooperating with the surface of roll 12 is a wiping element 28 which may suitably be made of soft rubber. Optionally, a doctor 29 may engage bottom roll 12 as shown in the drawing. Wet paper web 30 is brought into the nip, either in contact with felt 13 or roll 11 just prior to its entrance into the nip between rolls 11 and 12 and passes therethrough in contact with felt 13 and the surface of the upper press roll 11, as shown in FIG- URE 1. The paper leaving the nip between rolls 11 and 12 tends to follow the surface of top roll 11 for a short distance and then is removed therefrom by tension applied from subsequent parts of the machine. Roll 11 may be provided with a doctor 31 to remove fibers, starch lumps, etc. which may pick out of the paper surface onto the roll surface.
In operation, as best shown in FIGURE 2, water expressed from the paper web 30 by the action of the nip of rolls 11 and 12 is passed through felt 13 and into the open-mesh cells in fabric 20. As the fabric'parts from the surface of roll 12 on the exit side of the nip, the water transfers to the surface of roll 12 as a thin film, as shown at 33 in FIGURE 1.
The fabric 20 used for this purpose may suitably be of woven metal or plastic construction. While such fabric may consist of any weave, a plain weave or 4-harness sateen weave of various yarn weights are preferred. The
water removal capacity of the fabric depends on the void volume of the fabric mesh. If the water-carrying capacity of the fabric is exceeded by the quantity expelled'from the web, this water will collect as a pool on the ingoing side of the nip and such condition is to be avoided in selecting an appropriately designed fabric. Suitable fabrics for practicing this invention are shown in Holden et al., US. Patent 2,903,021.
As shown in FIGURE 1, the separation of paper web 30, felt 13 and fabric 20 occurs immediately on the exit side of the nip between rolls 11 and 12. This is a preferred arrangement which prevents re-absorption of water from the cells in the fabric into the felt or transfer of water from the felt to the paper web and represents the most efficient condition for water removal by this method. Thus, the fabric is trained for a short distance around the surface of roll 12, the felt is taken from the nip at a tangent to rolls 11 and 12, and the paper web tends to follow the surface of roll 11 to provide this desirable separation. However, improved dewatering is obtained as contrasted to plain presses of the prior art, even when 1y through nip 61 in its loop travel.
this separation is not provided and the web, felt and fabric travel in contact on the exit side of the nip.
When operating the apparatus at high speeds and with webs of unusually high moisture content, some water may be thrown off the surface of roll 22 inside the fabric run, as indicated in FIGURE 1. A water collection pan 32 and a cooperating wiping element 32A may be provided below roll 22 in the event that the quantity of water thrown out here is of sufficient magnitude to justify this step. Under ordinary conditions, the amount of water thrown off at this point is insignificant may be neglected for all practical purposes. At machine speeds in excess of 1500 f.p.m. and at drainage rates in excess of 40 lb. of water per ream of paper, water may be thrown off the surface of roll 12 by centrifugal forces immediately following the point of separation of the fabric and roll 12. Tray 27, as shown, is designated to catch such water.
The embodiment of FIGURE 3 is similar in most respects to that of FIGURE 1, with the exception that both felt and fabric are trained around the top press roll. Referring to the figure, rolls 34 and 35 are press rolls running in contact with a nip therebetween. Felt 36 is trained around felt idler rolls 37, 38, 39 and 40 to pass the felt through the nip between rolls 34 and 35, and is also provided with felt stretch roll 41 and felt guide roll 42. Likewise, fabric 43 is trained around fabric idler rolls 44, 45, 46 and 47 to run through the nip between rolls 34 and 35 in contact with felt 36 and is also provided with fabric stretch roll 48 of fabric guide 49. A water-collecting pan 50 is located adjacent to the surface of roll 34 on the outgoing side of the nip and is provided with a wiping element 51 to remove the water film from the surface of roll 34. Paperweb 52 is pressed into contact with the felt in the nip region and then, on the exit side of the nip, tends to follow the surface of roll 35 for a short distance before being pulled therefrom by tension applied to the web by subsequent parts of the machine, not shown. Felt 36 and fabric 43 are separated from each other and from the web on the exit side of the press nip, as shown in FIGURE 3. Roll 35 is provided with doctor 53 to keep its surface clean and free of accumulated fiber, etc. If desired, a shower 55 and suction box 56 may be provided for cleaning of the felt at a point remote from the nip area, as shown in the drawing.
It frequently happens that such felt-cleaning devices leave the felt with a relatively high water content and thus add to the load which must be treated or removed at the press nip between press rolls 34 and 35 of FIG- URE 3, or press rolls 11 and 12 of FIGURE 1'. In such instance, the provision of an additional pressing station to operate on the felt in contact with the fabric but without the paper web may be desirable. Such an arrangement is shown in FIGURE 4 and is contemplated as within the scope of this invention.
FIGURE 4 shows top press roll 57, center press roll 58, and bottom press roll 59 arranged vertically with their surfaces in contact and their axes parallel. Between rolls 57 and 58, the wet web 80, felt 62 and fabric 68 are passed through the nip 60 for water removal from the web. Water is likewise removed from felt 62 by passing the felt and fabric through the nip 61 formed between rolls 58 and 59 in the manner now to be described. Felt 62 passes around idler rolls 63, 64, and 65, felt guide roll 66 and felt stretch roll 67, passing through nip 60 and subsequent- Fabric 68 passes around fabric idler rolls 69, 70 and 71, fabric guide roll 72, and fabric stretch roll 73, passing first through hip 60 on the under side of the felt and then through nip 61 on the upper side of the felt to complete its travel. Wet web contacts roll 57 on the ingoing side of nip 60 and then follows this roll for a short distance after leaving the nip before being pulled therefrom by tension applied to the web by subsequent parts of the machine, not shown. Likewise, felt 62 is taken from nip 60 at a tangent to the rolls '57 and 58, while fabric 68 follows the surface of roll 58 for a short distance before leaving it to travel around idler roll 70. Water carried in the cells of the fabric at the exit side of nip 60 is left as a film on the surface of roll 58. It is removed from this roll by wiping or doctoring element 78 and is collected in pan 74 for removal from the system. In a similar manner, water expressed from the felt and carried in the cells of the fabric is deposited on the surface of roll 58 as shown at 77. This film of water is removed by flexible wiping element 79 and such water is then collected in pan 76 from whence it is removed from the system. Felt cleaning shower 82 and vacuum box 83 are provided, as shown in FIGURE 4-. These shower and vacuum elements are optional and are not needed for all grades of paper which may be treated on the wet press of this invention, although some grades may require their use. A cleaning doctor 81 may also be used in connection with roll 57 and likewise a wipe 84 may be used in connection with roll 59, as shown.
Referring to FIGURE 5, still another embodiment of the invention is presented wherein the dewatering principle of this invention is applied to both sides of the wet web simultaneously, and two pressing stations are employed. As shown, the wet Web 84 is carried by the wire 85 of a Fourdrinier papermaking machine around couch roll 86 to the pick-off roll 87 which is provided with a suction box 88. Pick-up felt 89 is trained around pick-off roll 87, guide roll 91, stretch roll 92, idler rolls 93, 94,
and with web 84 on its outer surfaces passes through the nip of press rolls 96 and 97. As the pick-up felt contacts the web at 90, the wet web is transferred to the surface of the felt by the action of suction box 88. Felt 89 with the wet web adhering to it then passes between the nip of press rolls 96, 97. A fabric 98 is trained to run inside the run of the felt 89, and passes around guide roll 99, press roll 96, idler roll 95, stretch roll 100 and is in contact with felt 89 at idler roll 93, it being understood that felt 89 and fabric 98 both travel in a counterclockwise direction. Water adhering to the surface of roll 96, being transferred thereto from fabric 98, is remover therefrom by flexible wiper 114 and collected in a pan 113 from whence it is removed from the system.
On the bottom side of the press formed by rolls 96, 97, a felt 102 is trained around stretch roll 103, guide roll 104 and idler roll 107 and is in contact with a second fabric 108 at idler roll 105, its run also passing in an interposed position through the nip between press rolls 96 and 97 and also through the nip of press rolls 111, 112, as shown. Second fabric 108 is trained to run inside the run of felt 102, passing around guide roll 109, stretch roll 110, and idler rolls 105, 106, its run also passing through the nips of both pairs of press rolls 96, 97, and 111, 112. Water removed from the web is transferred by the fabric to the surface of roll 97 at the first pressing station and water removed by the second pressing station is transferred from the fabric to the surface of roll 112. Roll 97 is provided with flexible wiper 116 which removes the water film from the roll surface and collects it in pan from whence it is removed from the system. Likewise, roll 112 is provided with flexible wiper 118 which removes the water film from the surface of this roll and collectsit in pan 117 from whence it is removed from the system. As top felt 89 wraps around idler roll 94, the web which has been partially dewatered by the action of press rolls 96 and 97, is raised above the surface of felt 102 as shown at 101. The second pressing station between rolls 111 and 112 is not provided with a top felt. The web, after leaving the nip of rolls 111 and 112 tends to follow the surface of top roll 111 and then is delivered to subsequent parts of the machine as indicated at 119. Thus, this arrangement permits dewatering of the wet web at three points, from both top and bottom of the web at the nip of rolls 96 and 97, and from the bottom of the web at the nip of rolls 111 and 112. Further, a straightthrough lead is'provided which avoids many of the complications of the prior art wet presses on machines operating with pickup felts.
Still another embodiment of the invention is shown in FIGURE 6, wherein a group of pressing stations are arranged around a central roll. In this embodiment, wet web 120, supported on Foudrinier wire 121 is led around couch roll 122 to the suction pick-up roll 123 which is provided with a vacuum chamber 124. A pickup felt 125 is trained around pick-up roll 123, idler rolls 128, guide roll 126 and stretch roll 127. It also travels around rolls 129 and 130 whereby the wet web is pressed against the surface of main press roll 133 and is transferred to the surface thereof as indicated at 160. If desired, this pick-up felt 125 may be provided with a washing shower 131 and a felt suction box 132.
Press rolls 134, 135 and 136 are arranged peripherally around roll 133 to provide three separate and distinct pressing stations around the circumference of roll 133. A press felt 140 is trained to travel in contact with fabric 148 at the press rolls 134, 135 and 136, around idler rolls 145, 143 and 144, guide roll- 142, stretch roll 141 and in contact with fabric 148 at idler rolls 146, 147. Fabric 148 is trained to run inside press felt 140 and is likewise trained through the nips formed between the main press roll 133 and press rolls 134, 135 and 136 in contact with press felt 140 as shown. Fabric 148 is also trained around idler rolls 146, 147, fabric guide roll 150 and fabric stretch roll 149 and is in contact with press felt 140 at idler rolls 143 and 144. It is withinthe scope of the invention for the fabric and felt to stay in contact with the wet web on the surface of roll 133 as indicated in the drawing, although somewhat higher efficiency in water removal may be obtained if the fabric is trained around idler rolls 158 and 159, as shown by the dotted lines in FIGURE 6 of the drawings. Water squeezed from the wet Web through the felt and into the fabric at the nip 137 between rolls 133 and 134 is transferred to the surface of roll 134 from whence it is removed by a wiping element 152 into catch pan 151 and then removed from the system. Likewise, water removed from the web through the press felt and into the fabric in nip 138 between rolls 133 and 135 is carried on the surface of roll 135 to wiping element 154 which removes it for collection in pan 153 from whence it is removed from the system. In a similar manner, water expelled from the web through the felt and into the fabric at the nip 139 between rolls 133 and 136 is transferred from the fabric to the surface of roll 136 from which it is removed by wiper 156 into collecting pan and then it is removed from the system. Following passage through nip 139 between rolls 133 and 136, the fabric, press felt and web are separated, as indicated in the drawing. The wet web follows the surface of main press roll 133 for a short distance and then is peeled away and delivered to subsequent parts of the machine as is indicated at 157. This embodiment shows use of common idler rolls 146, 147, 143 and 144 for both felt and fabric.
An embodiment of the invention which is particularly adapted to the dewatering of webs on high speed Yankee machines is shown in FIGURE 7. In this embodiment, a press felt 163 is trained to travel in contact with fabric 167 at the press rolls 164, 165 around idler roll 166 and thence around conventional stretch and additional idler rolls (not shown) to'form an endless felt belt. Wet web 162 is carried on felt 163 from the forming part of the machine (not shown) and is indirectly trained around rolls 164 and 165, whereby the wet web is pressed against and transfered to the surface of Yankee drying cylinder 170, which is internally heated. Fabric 167 is trained to run inside felt 163 around stretch roll 168, guide roll 169 and passes over rolls 164 and 165. Water expressed from the web, at the nip between roll 164 and Yankee dryer 170 travels through the felt into the fabric and is transferred by the fabric to the surface of roll 164 from which it is removed by wiping element 172 into pan 171. Likewise, water expressed from the web at the nip of Yankee dryer 170 and roll 165 is transferred through the felt and into the fabric and from thence onto the surface of roll 165 from which it is removed by the action of wiper 174 and collected in pan 173. The Web, after traveling around the Yankee dryer 170 is removed therefrom, for example, by a creping doctor 175, and delivered to subsequent parts of the machine as indicated at 176. In accordance with this embodiment of the invention, it is also contemplated that the Yankee dryer 170 could be provided with only one pressing roll, such as roll 164, and that roll 165 could be positioned so as to function as a stretch roll for fabric 167. Moreover, it is also within the comprehension of this invention that one or more additional press rolls similar to and functioning in the same manner as rolls 164 and 165, as shown in FIGURE 7, could be provided.
'Such machines producing tissue paper often run at speeds as high as 4000 feet per minute, with no dewatering by conventional vacuum of plain presses. Thus, this invention provides a means of reducing the drying load on the Yankee drying cylinder with its attendant benefits of lower steam consumption and/or higher operating speed.
The wet press of this invention has given very satisfactory drainage when installed as a third press following a twin suction press installation. consistencies up to 45% oven dry have been obtained as opposed to only 43% oven dry obtained with a vacuum press in the same location under similar conditions. Likewise, on a 27.5 (25x38500) ground-wood paper, manufactured at 1500/min., 42% consistency was reached compared to 40.5% with a suction press at equal press loading of 400 pounds/lineal inch. In this case, ingoing consistencies were equal for both press types.
The press of this invention permits operation at loadings well in excess of those generally used with vacuum presses. For example, experience has shown that a practical upper limit of 350400#/lineal inch is indicated for suction presses by considerations of shell size, mechanical strength, and undue wear on felts caused by the crowing of felts into the perforations of the suction press shell. Higher pressures on such presses result in more shadow-marking ofthe paper which is probably a consequence of the rubber cover of the plain roll pressing web and felt somewhat into the perforations of the shell of the suction roll which results in wet and dry spots on the surface of the sheet and can be accompanied by some redistribution of the fiber. As opposed to this limitation of vacuum presses, the wet press of this inventions permits operations to 600#/lineal inch and even higher and water removal continues to be increased as pressures are increased.
In still another operation of the press of this invention as compared to a conventional plain wet press, it was found that consistency of the web could be increased from 39% to 44.5% and the reduced drying load on the balance of the machine permitted an increase in speed from 650 ft./min. up to 800 ft./min. The new limit was brought about by machine drive capacity and not through drying limitations.
The amount of water which may be removed by a fabric when operated according to this invention is roughly proportional to the void volume of the fabric. For practical purposes, the limit of fabric capacity is reached when the amount of water squeezed out of the wet web begins to pool ahead of the press nip and is no longer carried through the nip.
When comparing the wet press of this invention with a plain wet press, a further important distinction becomes evident. Since, in a plain press, water expelled from the web must travel through the felt and run down the surface of the press roll in a direction opposite to the travel of the roll, a practical upper speed limit normally is something less than 1000 ft./min. for plain presses. By operating with a fabric within' the run of the felt on a plain press as taught by this invention, speeds as high as 2400 ft./min. have been used in practice with no indication of an upper limit. Likewise, there appears to be no effective lower limit to the speed at which the fabric and felt Work effectively in removing water from a wet web.
While, as stated previously, somewhat better results are obtained-when the wet web, the felt and the fabric are separated immediately following a pressing nip, the run of felt and fabric together after leaving a nip gives about of the improved otherwise obtainable with the invention provided that both felt and fabric are pulled off the fabric contacting roll immediately at the nip exit. For this reason, it is within the scope of this invention to train a press felt and fabric around the same group of rolls without any separation of the two at any point in their run. And in this connection, as is evident from the above description and the drawings, the felts and fabrics are run in the directionof their respective press rolls and at the same speed of such rolls. Likewise, it is contemplated that a duplex weave structure may be provided wherein the top surface is a plate finish press felt and the bottom surface is an open mesh fabric of substantially incompressible material and the two structures are interwoven into an integral unit which behaves as one element. Such an element would function in the same way as other embodiments of the invention as set forth herein.
While certain embodiments of the invention have been presented herein in detail, it is understood that the invention embraces all modifications which would be apparent to one skilled in the art, and all equivalents which come with in the scope of the appended claims.
What is claimed is:
1. A process for removing entrained water from a moving wet web of paper and the like comprising:
passing said web together with a felt and a fabric through the nip of a pair of press rolls,
said felt comprising a finely-woven water receivingtransferring material, said fabric comprising a synthetic resinous material having uniformity of porosity necessary for passage of water under nip pressure, said fabric material being interposed in said nip between said press rolls and said felt, concomitantly transferring said water from said felt through said fabric onto the surface of one of said press rolls by rolling pressure from said press rolls, separating said web, said felt and said fabric at the exit side of said nip,
said fabric following the surface of the press roll with which it is in contact for a sufficient distance to effect transfer of water from said fabric to said press roll surface, and thereafter removing said water from said press roll surface.
2. A process according to claim 1 in which the fabric is in the form of a continuous loop.
3. Apparatus for a papermachine for removing entrained liquid from a moving web of paper and the like comprising:
a pair of cooperating press rolls having a nip therebetween,
means for driving said press rolls to move said web through said nip at a rapid rate of speed,
a fabric porous to liquids extending through the nip of said rolls,
said fabric being endless and characterized by having a' woven mesh structure, said fabric being sufficiently trained around one of said'rolls to transfer water pressed out by said rolls to the surface of the said one of said press rolls, means for removing water from the surface of said one press roll, and
means for separating said web and said fabric at the exit side of the nip of said press rolls.
4. Apparatus according to claim 3 wherein the web and fabric are passed through said press rolls with a waterreceiving-transferring felt material, said material being interposed between said web and said fabric.
5. Apparatus for a papermachine for removing entrained liquid from a moving web of paper and the like comprising:
a pair of cooperating press rolls having a nip therebetween,
means for driving said press rolls to move said web through said nip,
a fabric porous to liquids extending through the nip of said rolls,
said fabric being endless and characterized by having a woven mesh structure for receiving liquid from said web,
said fabric being sufiiciently trained around one of said rolls at the exit side of said nip, so as to transfer 10 a portion of said liquid from said fabric to the said one of said rolls, means for removing water from said fabric at the exit side of said nip, and means for separating said web and said fabric at the exit side of the nip of said press rolls.
References Cited by the Examiner UNITED STATES PATENTS 1,600,509 9/1926 Millspaugh 162-360 2,618,205 11/ 1952 Heys 16236O 2,672,078 3/1954 Hornbostel 162-360 0 2,869,437 1/1959 H-ornbostel et al. 162360 3,093,535 6/1963 B-r-auns et al. 162358 FOREIGN PATENTS 472,924 4/1951 Canada. 586,264 11/ 1959 Canada. 1,198,432 6/1959 France.
527,130 6/ 1931 Germany.
DONALL H. SYLVESTER, Primary Examiner. MORRIS 0. WOLK, Examiner.
J. H. NEWSOME, Assistant Examiner.
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|US5961735 *||5 Jun 1997||5 Oct 1999||North Carolina State University||Method of cleaning papermaking felts with enzymes|
|US6103062 *||1 Oct 1998||15 Aug 2000||The Procter & Gamble Company||Method of wet pressing tissue paper|
|WO2003046279A1 *||27 Nov 2002||5 Jun 2003||Voith Paper Patent Gmbh||A pressing felt|
|U.S. Classification||162/199, 162/272, 162/359.1, 162/360.2, 139/383.00A, 162/205, 162/DIG.700|
|International Classification||D21F3/02, D21F1/00|
|Cooperative Classification||D21F3/029, D21F1/0027, D21F3/0281, Y10S162/07|
|European Classification||D21F3/02D, D21F3/02E, D21F1/00E|