US 3434922 A
Description (OCR text may contain errors)
March 25, 1969 D. A. ELY 3,434,922
PRESS ARRANGEMENT Filed Oct. 28, 1965 "VENTOR.
[5 Y ATTORNEYS United States Patent Ofice US. Cl. 162-303 5 Claims The instant invention relates to paper making machinery, and more particularly, to a lightweight or tissue forming paper machine producing web of high quality.
Modern-day paper making machines include various dilferent constructions which are adapted for making one type of paper web or another. One category of paper machine is known as the so-called Yankee machine, which involves the use of a Yankee dryer. The Yankee dryer is a large diameter roll under which a moist web is pressed or pasted, after the moist web has ordinarily undergone comparatively nominal or minimum pressing for purposes of dewatering. The web itself is ordinarily a lightweight type of web which does not respond favorably to most types of presses and which is most advantageously dewatered during its travel on the heated Yankee dryer surface. On the other hand, the paper web must be formed initially using a forming wire or other forming means so as to have a coherent fibrous web that will remain on the surface of the Yankee dryer for perhaps 270 of rotation on the dryer surface, so as to obtain a relatively dry web even operating at comparatively high speeds. Moreover, the lightweight paper web must be formed with a minimum of rough handling of the web because of its generally delicate nature.
The instant invention relates to an improvement in Yankee dryer machines, and more particularly, an improvement in machines for the formation of comparatively delicate lightweight paper web.
Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following disclosure and the drawings attached hereto and made a part hereof.
ON THE DRAWINGS FIGURE 1 is an essentially diagrammatic view in elevation of a paper machine embodying the instant invention; and
FIGURES 1A and 1B re essentially fragmentary diagrammatic views of for ing sections which may be used in the instant invention to replace the forming section shown in the view of FIGURE 1.
AS SHOWN ON THE DRAWINGS A looped forming wire 11 is shown traveling around a relatively large breast roll 12 and couch roll 13, which define therebetween a downwardly inclined web forming run 11a. The remainder of the looped forming wire travels over guide rolls 14 and 15 which assist in maintenance of the desired tension, traveling speed, etc. for the forming wire, in generally the conventional manner of mounting forming wires. In the particular instance, however, the active or top run 11a of the instant forming wire 11 is downwardly inclined at substantially an angle of 45 from the horizontal. This angle is preferred for the downward incline of the active run 11a, but the instant invention may be carried out using a downward incline for the top wire run 11a within the range of substantially to 70 from the horizontal.
At the upstream or top side of the downwardly inclined wire run 11a there is mounted a conventional stock inlet indicated essentially diagrammatically at 20. The inlet is provided with conventional stock feed means (not shown) to the end that a substantially uniform high speed jet-stream of entangled fibers in aqueous 3,434,922 Patented Mar. 25, 1969 suspension may be fed out of the inlet slice indicated diagrammatically at 21 and onto the upstream end of the forming wire run 11a. The forming wire run 11a is mounted to travel at substantially the relatively high jet-stream speed of the stock from the slice 21 and adapted to receive the stock thereon at substantially the immediate oif-running side of the upper (breast) roll 12. A large saveall 16 is shown essentially diagrammatically, positioned just beneath the top wire run 11a and between the breast roll 12 and the couch roll 13 in order to collect substantial volumes of water flowing freely from the stock suspension through the forming wire run 11a. It will be appreciated that in the case of comparatively lightweight paper web formation there is a substantial amount of water that must be handled and this water willflow quite readily through the forming wire 11a during web formation (not only at the time of initial web formation in the upstream region of the immediate discharge from the stock stream jet 21 but also farther down along the downwardly inclined reach 11a, because the lightweight web will offer less resistance to the free flow of water through the same and through the forming wire 11a in the saveall 16). Although the relatively lightweight web forming on the top wire run 11a offers relatively nominal resistance to the flow of water therethrough and into the saveall 16, it must be appreciated that the weave of the wire run 11a plus the deposition of fibers thereon will alford a certain amount of resistance to the water flow through the wire run 11:: and into the saveall 16, to-the end that there will be a pool of aqueous suspension traveling along the top of the wire run 11a for at least a short distance (e.g. down to ap proximately 11b in FIGURE 1).
The paper machine of FIGURE 1 also is provided with a Yankee dryer indicated generally at 30, which is a comparatively large metal roll that is provided with a smooth (mirror) finish for receiving and dewatering the web thereon and is also generally provided with means for heating the interior thereof (indicated diagrammatically at H) in order to accelerate the dewatering of the web moving on the traveling Yankee dryer surface. This structure is essentially conventional, as also are the doctors 31 and 32 shown at the bottom side of the Yankee dryer 30 Which are used for maintaining continuously a clean dryer surface.
Also shown in FIGURE 1 is a looped traveling felt 40 which is mounted on a plurality of felt guide rolls indicated generally at 41, plus a tensioning roll indicated at 42 for maintaining the desired tension on the traveling felt 40. The felt 40 is also shown passing between a pair of conventional wringer or press rolls 43, 43 to dewater the same over a suction box 44 acting on the active surface of the felt 40 for purposes of conditioning such felt surface. These last-mentioned elements are also conventional for felt operation and need not be described in further detail herein.
The felt 40 travels around a curved solid surface 45, which is shown as the solid roll or solid felt guide roll 45 positioning and turning the felt at substantially the immediate olf-running side of the stock slice 21. The solid roll 45 positions the felt 41 in closely spaced relation to the downwardly inclined wire run 11a, but there is a definite spacing between the wire run 11a and the felt 40 as it travels around the solid roll 45 through a curvate (convexly curvate) converging path and against the top side of the stock jet stream that is being fed onto the top run 11a of the forming wire. Downstream from the solid guide roll 45 there is positioned a second solid or plain roll 46 within the loop of the felt 40 and the second solid roll 46 is shown urging the felt 40 into very close running relation with the downwardly inclined wire run 11a. In fact, a felt reach 40a from the guide roll 45 to the guide roll 46 is shown downwardly inclined and convergingly directed relative to the downward run of the forming wire 11a, such that the stock jet stream fed from the slice 21 onto the forming wire run 11a in substantially the region of the upstream felt guide roll 45 will have lost a sufficient amount of water to have effectively formed a moist paper web at substantially the location 11b on the forming wire run 11a opposite the solid roll 46.
The solid roll 46 presents a rotary surface substantially like the solid rotary surface of the upstream guide roll 45 that is traveling at substantially the same peripheral speed for the felt 40, which speed is, in turn, substantially the speed of the stock stream jet in the slice 21 and the speed of the traveling forming wire run 11a. The felt 40, however, at the off-running side of the solid roll 46 is comparatively Wet and the solid roll 46 functions to develop subatmospheric pressure at its immediate off-running side 46a, which in turn acts against the inner periphery of the felt 40 in this region so that the felt 40 will tend to lift the web W from the downwardly inclined wire run 11a in the region 11b. The felt run 40b that extends also in the generally downward incline from the solid felt roll 46 serves to retain the web on the underside thereof until it reaches a pasting roll 47 that is also within the loop of the felt 40 and which is a suction roll that pastes the wet web onto the underside of the Yankee dryer 30. The pasting roll 47 is not necessarily a suction roll but it is preferably a suction roll because it will handle a relatively substantial amount of water at this location and it is not desired to build up substantial quantities of water at the oncoming side 47a of the pasting nip N-l defined by the suction roll 47 and the Yankee dryer (for the reason that a buildup of an excessive amount of water, i.e., in the form of a pool or otherwise at the oncoming side of the nip N1 may cause damage to the web just before it is pasted onto the Yankee dryer 30). Also, the suction roll 47 preferably removes a substantial amount of water from the felt at the region of the nip N-1 so that a second press roll 48 also wrapped by the felt 40 may function to facilitate both retention of the web W on the Yankee dryer surface and a certain amount of dewatering thereof at a nip N2 downstream from the nip N-l (or in the direction of movement of the web W along the upstream side of the Yankee dryer 30).
It will be appreciated that the wringer rolls 43, 43 and/ or the felt conditioner 44 will serve to bring the water content of the felt 40 into a condition in which it is most receptive to receive a certain amount of water from the stock flowing on the forming wire 11a, so that some dewatering of the stock may take place merely by absorption of water into the body of the felt 40 during the converging felt run 40a from the guide roll 45 to the guide roll 46. The amount of water thus absorbed by the felt is perhaps not extremely significant from the point of view of overall water removal from the aqueous stock suspension, but it is significant from the point of view that the felt in the run 40a is not intended to resist acceptance of water in this region, nor is it intended that the felt run 40a should return water back to the stock stream on the downwardly inclined wire run 11a. Instead, the converging felt run 40a will serve to expedite dewatering of the aqueous stock suspension on the forming wire run 11a not only by the reception of at least a nominal amount of water into the body of the felt 40 but also by virtue of the fact that the felt 40 is pressed against the stream of stock flowing on the wire run 11a so as to accelerate dewatering of the stock through the forming wire 11a and into the saveall 16. The control of the rate of such accelerated dewatering is important so that there will be a minimum and/or substantial elimination of defects in the web thus formed.
On the other hand, the felt 40 should be relatively wet at the off-running side of the guide roll 46 so that it is unable to receive air rapidly in the neighborhood of the low pressure region 46a and the web W will then adhere quite well to the underside of the felt during the downwardly inclined run 4% from the takeoff roll 46 to the pasting suction roll 47. This is preferably a downwardly inclined run 40b so that the web will adhere better to the underside of the felt run 40b in this region (and will not have to overcome gravity forces among others in its retention onto the underside of the felt run 40b). For this purpose the felt run 4012 should be downwardly inclined preferably at least about 5 to 15 or 20 from the horizontal. The pasting (suction) roll 47 will also preferably have at least a low vacuum area 47]) which will extend from substantially the bottom of the suction roll 47 to substantially the nip N1 so that the web will also be readily retained on the surface of the felt 4t turning about the suction roll 47 and into the nip N-1.
In connection with the downward incline of the wire run 11a and the convergingly downward incline of the felt run 40a, it will be appreciated that the rapid flow of the stock stream from the slice jet 21 will serve to maintain a body of water in the area of convergence C between the wire run 11a and the downwardly inclined felt run 40a, such that a hydraulic head may be continuously maintained in this zone of convergence C and pressure on the stock moving therein will be readily controlled and maintained. If the stock stream rate from the jet 21 is too slow and/ or the traveling speeds of the felt run 40a and/or the wire 11a should be too rapid in a generally horizontal area of convergence C, it will be appreciated that there might be a tendency to draw air into the area or zone of convergence C and/or there might be a tend ency to have this area empty partially from time to time because of loss of stock, all of which would result in defects in the paper web particularly during the critical web forming period in this zone of convergence C. On the other hand, because of the downward incline of the two runs 11a and 40a, a hydraulic head is maintained substantially continuously and constantly in the zone of convergence C and web formation takes place under ideal conditions, particularly for the lightweight high speed operation here contemplated. It will be appreciated that the felt run 40a is also at a downward incline, as contrasted to a substantially vertical run, so that it will press against a stock stream normally flowing in the downwardly inclined wire run and cooperate with gravity forces, the hydraulic head, etc., to apply pressure to the top side of the stock stream and thus expedite web formation on the wire run 11a.
Referring to FIGURE 1A, it will be seen that elements having substantially the same structure and function as those shown in FIGURE 1 are designated by the same reference numerals in the series. Thus the bottom forming wire run 111a is trained over an upstream breast roll 112, moving downstream at an incline over a saveall 116, which is equipped with foils or wipers 116a, 116a within the saveall 116 for purposes of facilitating dewatering and tending to wipe droplets and/or bodies of water that might be inclined to hang on to the underside of the forming wire 11a. Also, the inlet 121 feeds the stock stream between the forming wire 111a and the converging felt run a just upstream from the solid guide roll 145. The guide roll presents a co-moving solid curved surface for guiding and traveling with the felt 140, but it will be appreciated that an open faced roll could be used in the position 145, although such a roll would ordinarily be more expensive and it is not necessary in the particular arrangement here shown. The converging felt run 14tla moves down around a roll 150, which corresponds to the previously described roll 46 in that it effects substantial completion of the convergence of the felt run 140a with the wire run 111a, thus carrying out the previously described function of the solid roll 46. Again, the instant roll may be an open-faced roll and in this particular instance it may have some additional useful function as an open-faced roll. But preferably it is a solid roll 150 which will substantially preclude the formation of a water layer on the inner periphery of the felt 140, for the reason that water removal from the inner periphery of the felt 140, if a water layer were formed thereon, would require some auxiliary equipment and would thus increase the overall expense of the machine. Instead, the bulk of the dewatering of the stock and the bulk of the formation of the moist paper web is accomplished by the time the converging felt run 140a passes beneath the plain roll 150, but a second plain or solid roll 151 is here shown defining still another felt run 140a that is maintained in very close running relation, and against the moist felt, on the downly inclined wire run 111a essentially for the purpose of facilitating some additional dewatering of the moist web in the brief region of travel opposite the felt run 1400. I111 mediately thereafter the solid roll 150 in cooperation with the moist downwardly inclined felt run 14Gb serves to carry the web W onto the Yankee dryer, for example, at the nip N-l already described in connection with FIGURE 1. The essential purpose of the arrangement shown in FIGURE 1A is the showing of a certain amount of versatility which the instant machine affords, at a very nominal expense, for the reason that the plain rolls 150 and 151 are not expensive to install and/or to mount in the desired selected spacial relationship to the downwardly inclined wire run 111a.
Referring to FIGURE 1B, it will be seen that still another aspect of the advantage just mentioned in connection with the embodiment of FIGURE 1A is shown. In other words, still additional solid rolls may be used, at very nominal expense and with ease of adjustment and versatile function in the arrangement of FIGURE 13, In FIGURE 1B the elements corresponding substantially to those shown in the previous views are designated by the same reference numerals in the 200 series. It will be seen that the wire run 21111 is again inclined downwardly and there is provided a converging felt run 240a between an upstream roll 245 and a roll 250 at substantially the region of complete convergence between the downwardly running felt run 240a and the downwardly running wire run 211a. Also, the downstream roll 251 corresponds to the roll 151 shown in FIGURE 1A. An upstream guide roll 252, however, is positioned substantially midway in the downwardly inclined felt run 240a between the upstream roll 245 and the roll 250 just mentioned. The additional guide roll 252 may be an open or a closed roll, but again it is preferably a closed or solid roll and its function is essentially that of maintaining a slight convexly rounded converging contour to the downwardly inclined felt run 240a. Thus if dewatering is taking place extremely rapidly through the downwardly inclined wire 211a, then it may be desirable to use the roll 252 to cause the felt run 240a to follow more closely and press against the top surface of the stock stream flowing on the downwardly inclined wire run 211a. It will be appreciated that the rolls 150-151 and/or the rolls 250-251 and 252 function essentially as solid means within the loop of the felt 40, 140, 240 downstream of the felt guide 45, 145, 245 for urging the converging felt run downwardly into the desired gradual convergence with the wire run 211a. Even the felt movement in the region 140c and/or 2400 does involve additional convergence of the felt with the wire, for the reason that the moist paper web is still undergoing the process of dewatering in this region. The advantage here is that the moist web is passed only gently by the traveling felt in these critical regions of formation and the web is not subjected to the pressures of a conventional press nip at any time during its formation and/or until it is already placed upon the Yankee dryer surface. As previously indicated the web is pasted onto the Yankee dryer surface at approximately the nip N-l (shown only in FIGURE 1) and dewatering thereof takes place immediately by virtue of the heat of the Yankee dryer 30. A second press nip N-2 is shown as an optional embodiment which may be used to apply a certain amount of pressure to the web W, after it has already undergone some dewatering on the surface of the Yankee dryer 30.
The nip N-2 may be used to apply dewatering pressure,
but preferably it is used essentially to assure that the web W remains pasted on the surface of the Yankee dryer 30. The heat of the dryer 30 does tend to cause evaporation of water at the very surface of the dryer 30 and along contiguous faces of the dryer surface 30 and the web W, such that a certain amount of volatilization of water in this region may cause the web to tend to lift from the surface of the dryer and the roll 48 at the nip N4 functions primarily to assure that this undesirable effect is not obtained. It will thus be seen that actual pressing of the web primarily for purposes of dewatering the same is not required at any position in the Yankee dryer machine shown in the instant invention. If such pressing should be desirable, however, additional pressure could be applied at the roll 48, but in instances in which the application of such higher pressures is not desirable (which is generally the case in the practice of the instant invention), then it will be appreciated that merely the function of assisting in retaining the web on the surface of the dryer 30 is carried out at the roll 48.
It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.
I claim as my invention:
1. In a paper machine, in combination, a Yankee dryer, a stock inlet, a looped traveling forming wire having a downwardly inclined run receiving stock from the inlet and forming a wet web on such run, a looped traveling felt, a felt guide within the felt loop presenting a curved smooth surface for guiding the felt into closely spaced relation to said wire run adjacent the stock inlet for receiving a stock stream between the wire run and felt, roll means within the felt p downstream of such felt guide for urging a run of felt downwardly from such guide into gradual convergence with said wire run during web formation thereon and then away from the wire run with the formed wet web adhering to such felt run, and pressuredewatering and pasting rolls within the felt loop downstream of such roll means for pasting the wet web onto and pressure-dewatering the web against the Yankee dryer surface.
2. The paper machine of claim 1 wherein the pasting roll is a suction roll defining a suction press nip with the Yankee dryer.
3. The paper machine of claim 1 wherein the roll means within the felt loop is a solid roll.
4. The paper machine of claim 1 wherein the roll means within the felt loop is a solid roll wherein the felt guide is a solid roll, and wherein the pasting roll is a suction roll defining a suction press nip with the Yankee dryer.
5. The paper machine of claim 1 wherein the roll means within the felt loop comprises a pair of solid rolls holding the felt run briefly against the wet forming web on the wire before separating the web therefrom.
References Cited UNITED STATES PATENTS 2,911,039 11/1959 Hornbostel et al. 162303 3,224,928 12/1965 Lee et al. 162-303 X 3,236,724 2/ 1966 Wahlstrom 162-303 X 3,262,841 7/1966 Embry 162303 X DONALL H. SYLVESTER, Primary Examiner. A. C. HODGSON, Examiner.
U.S. Cl. X.R. 162-203, 348