US2264169A - Vacuum producing apparatus for paper making machines - Google Patents

Description

E. POIRIER Nov. 25, 1941.

VACUUM PRODUGNG APPARATUS 'FOR PAPER MAKING MACHINES Filed Apri: e, 1938 2 sheets-sheet 1 Nov. 25, 1941. POIRIER VACUUM PRODUCING APPARATUS ,FOR PAPR MAKING MACHINES Filed April 6, 1938 2 Sheets-Sheet 2 ATTORNE Patented Nov. 25, 1941 UNITED STATES PATENT OFFICE VACUUM PRODUCING APPARATUS FOR PAPER MAKING MACHINES 8 Claims.

This invention relates to paper making and more especially to the apparatus used in paper making machines to extract water from the sheet. While the invention will be herein disclosed as applied more especially to the problems involved in a Fourdrinier paper machine, it will be understood that it is also applicable to other types of paper machines and to other units used in the manufacture of paper.

As is Well understood by those skilled in this art, the stock delivered =to the wire of a Fourdrinier machine contains an extremely high percentage of water and a correspondingly low proportion of iiber, llers and other solid constituents. A large percentage of this water ilows through the wire as it; passes over the table rolls and more of it is extracted by the suction boxes. Control of the extraction of water from the sheet is highly important for the proper felting of the fibers together to form the sheet or web and to the delivery of the web to the dandy roll, couch roll, and subsequent devices and mechanisms which operate on it, with the proper degree of moisture or wetness necessary to enable these devices to perform the functions for which they are intended. For example, in the case of the dandy roll there is a fairly denite proportion of water in the sheet which is better for the operation of this roll than either a smaller or larger percentage. The operator customarily produces the desired result by properly spacing the water line from the dandy roll, and he tries to maintain those conditions necessary to hold this water line at a substantially fixed point. The term Water line is well understood by anyone skilled in this art. In a general way it indicates the line extending across the sheet where the water has left it to such a degree that a very noticeable and relatively sharp diierence in the surface appearance of the sheet is readily seen. If the sheet becomes slower, that is, more dense or releases its water more slowly, the water line moves down the wire and the machine tender makes suitable changes, such as increasing the vacuum or de creasing the proportion of make-up water, to correct this difllculty. If the sheet becomes freer," it loses its Water more,` quickly, the water line moves up the wire and the operator makes other adjustments to correct this condition. A large part of the skill involved in properly tending a paper machine consists in making those adiustments necessary to properly control the position of the water line.

The present invention aims to reduce much of the care, skill and attention required in this op- It is practically the universal custom to pro-V duce the working vacuum required in a paper machine by means of power driven pumps, and the expense involved in maintaining a vacuum by this method is a very substantial item. While it has been proposed heretofore to produce this vacuum barometrically by running the water from the boxes through a so-called drop leg, the lower end of the leg being placed in a well, tail race, or similarly located so that it will be sealed against the entrance of air, this system produces a vacuum varying so greatly that it has not been depended upon to any substantial degree in recent years, although it was probably the iirst method used of producing the vacuum required for this purpose. As heretofore employed, such.

a system has itself been responsible for much of the trouble in properly controlling the water line. Of course a drop leg is still used in pump systems to carry away the water extracted by the boxes, but it is depended upon only in rather rare instances to produce the working vacuum. It is one of the objects of the present invention to overcome the diiiiculties heretofore experienced in using systems of thischaracter and adapting them to` present day paper making methods and machines.

The same vacuum conditions exist and essentially the same problems are presented in other machines carrying a wet web of paper or pulp from which the Water is extracted by vacuum boxes, vacuum rolls, and the like. The present invention is applicable to situations of this type and accordingly, the term vacuum box or water box will be herein used in a generic sense to include vacuum rolls and similar devices to which the invention is applicable.

The nature of the invention will be readily understood from .the following description when read in connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims.

In the drawings,

Figure 1 is a side view, largely diagrammatic in character, illustrating an apparatus embodying the present invention;

Fig. 2 is a vertical. sectional view through the upper portion of one of the valves shown in Fig. 1:

Fig. 3 is a vertical, sectional view through a Fig. 4 is a vertical, sectional view of another I form of vacuum header which may be used in place of thatshown in Fig. 1; and

Fig. is a plan view of parts of the apparatus shown in Fig. 4.

Referring rst to Fig. 1, the apparatus there shown comprises a vacuum box 2 like those commonly employed in Fourdrinier machines, the paper making wire 3` running over the top of this box and the web W being supported on it. Usually several of these boxes are arranged side by side so that the wire runs over them successively. Also, as in the usual constructions, the box is equipped With two sliding heads 4 arranged to be adiusted longitudinally of the box by any suitable construction to accommodate the width of the -web being made. From the left-hand end of the box, a water discharge pipe connection 5 leads to a vacuumcasing or header 6 from which a drop leg 'I extends downwardly into one compartment of a well or overilow box 8 equipped with the usual adjustable Weir I0. The water discharged from the pipe flows from this compartment over the weir into another compartment from which the Water is taken away by the pipe I2. In some cases the water flows directly from this overilow box into the river, while in other instances it is taken away by a pump. In the latter event, it is desirable: to mount a float controlled shut-off device, such` as that shown at I3, Where it will close the end of the pipe in the event that .the compartment from which it draws Water becomes nearly empty. Normally the float I4 holds the shut-off plate I3 in an elevated posi- K tion and leaves the intake end of the pipe I2 completely open. l

Connected between the box 2 and header 8 is a valve I5, best shown in Fig. 4, comprising a valve plunger I6 mounted on suitable guides to move vertically toward and from a seat I1. Connected with it is a lever I8 mounted on a rock shaft I9 and carrying a weight 20 adjustable lengthwise of the lever. v

The water extracted from the web by the box 2 and owing through the drop leg creates a partial vacuum in the box which is utilized for normal operating purposes. Thedegree of vacuum so maintained depends primarily upon the head of water in the drop leg which, in turn, depends partly upon the volume of water discharged from the box, partly on the volume of air flowing through the sheet W passing over the box, and to some degree, also, on the-rate of release of the air entrained with thewater as it flows through th drop leg and is discharged.

I have found that if the flow of air and water is yieldingly throttled or restricted between the box and the level of the water in the drop leg, the fluid pressure conditions maintained in the box will be improved very materially. Speciilcally, the intensity or amplitude of the variations will be reduced, and those variations which do occur can be made to assist in holding the water line at the desired point. f

The reasons for this advantageous result are very obscure, but it has been determined in actual practice that this arrangement does maintain automatically very much better vacuum condioperate to produce an opening movement -of the valve. This action is yieldingly resisted, counterbalanced, or overcome by the weight 20, depending upon its adjustment. Thus the valve plunger I6 floats between the forces so acting upon it. Considering the b ox immediately after the dandy and assuming the web changes `from a fairly free to a slower condition, with a corresponding increase in density or thickness, which practically always goes with a slower sheet, the fact that the top of the box then is sealed more effectively by the sheet, and thus reduces the volume of air leaking through it, tends to increase the degree of vacuum in the box. Also, an increase in the volume of water taken out by the box, which usually accompanies this condition, tends to raise the vacuum. These are helpful factors to a degree because a higher vacuum is needed to hold the water line in the desired position, but they must be controlled in order to produce this result. Such a control is afforded by the valve plunger I6 which is lowered by these changes in iluid pressure conditions but to a degree governed by the weight 20 so that it still throttles the flow through it and therefore controls the rise in vacuum.

On the other hand, if we assume that the sheet becomes freer, with the accompanying tendency for it to release its water more freely to the table rolls, which is characteristic of a free sheet, then the more rapid admission of air to the box will reduce the vacuum. At the same time the re duced volume of water extracted by this particular box also reduces the vacuum. The valve plunger I6 rises toward its seat I1 due to both of these factors and thus increases the resistance to ow of iluids through it. While, therefore, the vacuum in the box is lowered at this time and such an action is desirable in order to hold the water line in its normal and desired position, nevertheless such an action is controlled by the valve and the vacuum is not allowed to drop excessively or to be lost entirely, as it probably would be if the valve were not used.

Thus the valve exerts a stabilizing iniluence on the conditions affecting changes in vacuum in both the header and the box. Adjustment of the weight 20 to increase its leverage produces a reduction in vacuum in the box if other conditions remain unchanged, and vice versa. The degree of vacuum maintained in the header is indicated by the gage 2|.4 This same arrangement is equally useful on the other boxes. Also, when a dandy is not employed, it is still desirable to hold the water line in substantially a xed position. I have found that by properly adjusting the weight 20 the vacuum maintained may be made Ato change almost directly in proportion to changes in the characteristics of the web, and this is a highly desirable condition.'

In prior constructions the drop leg has consisted of a single pipey which necessarily is made of ample dimensionsV to carry the maximum volume of water that can reasonably be expected tions in a system of this type than can be realized without it, particularly in some boxes. It will be evident that when the apparatus is in operation both the vacuum conditions in the neighborhood of the valve and the now of waterthrough it, co-

ever to be discharged from the box. lThis fact is a source of variation in the degree of vacuum that will be maintained in the box and consequently is a factor in shifting the water line. It will be evident that if the sheet being made is of such a character that the volume of water delivered by the box is small, it will not be able to nll a large -drop leg to the same height, other conditions being equal, as it would a small leg. Consequently, if the volume of air leaking through the sheet were to remain constant while the lvolume of water decreased, the vacuum in the box would correspondingly decrease. Of course such a condition rarely, if ever, happens, but the limitations of a drop leg of this character nevertheless are responsible for much of the undesirable variation in vacuum that has attended prior attempts to rely solely on a drop leg to produce the working vacuum.

I have found that variations in the degree of vacuum produced by such changes in conditions as those just described can be greatly reduced by making the drop leg in sections, somewhat as shown. In the particular instance illustrated it may be assumed, for example, that the sections or conduits a and b each consist of two inch pipes, whereas the section or conduit c consists of a four inch pipe. If now the volume of water -is so reduced that the pipe a carries it all, then the degree of vacuum maintained in the casing- 6 will be held at a higher value than it would if this pipe were, say, six inches in diameter for the reason that the head of water maintained in itV would rbe considerably higher in the former case than in the latter. And, as above pointed out, this matter of hydraulic head is an extremely im portant factor in determining the degree of vacuum that will be maintained in the casing at any instant. Preferably baflies 22, Fig. 1, are provided in the bottom of the casing E, dividing this part ofthe casing into three compartments from which the respective sections of the drop leg lead. These bailles assist in controlling the flow of water, directing a small flow yalmost exclusively into the section a, and when the rst baffle is overfiowed preventing any substantial flow into the compartment farthest from the pipe connection until the head of Water in the casing has risen so that both baliles are submerged.

From the foregoing it will be evident that with this arrangement the number of sections or conduits of the drop leg which are utilized at any instant to carry away the Water from the box 2 will change automatically with changes in the volume of water discharged from the box. In other words, when the volume is so small that a single section of the drop leg will take care of it,

then practically all of the discharge will take place through that section. As soon, however, as the volume of water increases beyond the capacity of the first section, one or more of the other sectionsv will be brought into operation automatically by such an increase. Upon a decrease in volume of water the drop leg sectionsactually in operation will decrease successively, only those remaining in operation at any time which are necessary to conduct the volume of water being used at that time.

In order to provide an increase in vacuum when it is needed, as for example, in starting up, or at any other time, I prefer to run another vacuum line 23 into the casing 6 from any convenient supplemental source of vacuum pressure as, for example, to the vacuum line 24 running to the couch roll. It is sometimes desirable to include a valve 25 in this line which may either by a gravity check valve or, more preferably, a valve of that general nature in which the movable valve element is backed up by a spring which can be adjusted, the valve in either event permitting a iiow from the casing 6 toward the vacuum header 24 but preventing iiow in the opposite direction. This valve may be set to open whenever the vacuum ln the casing 6 is substantially lower. than that in the vacuum line '26.

n Thus it creates a vacuum in the casing 6 and box 2 during the starting period and increases the vacuum in these members whenever it falls below substantially a predetermined value for any reason.

Preferably the tip d, Fig. 1, of the vacuum pipe 23 is turned at an angle to the main portion of the pipe and is connected with the valve 25 through a coupling 26. Thus this tip can be adjusted so that its open end will practically always be above the lev'el of the water in the casing 6.

In another arrangement shown in Fig. 2, the 'pipe 23', corresponding to the pipe 23 shown in Fig. 1, is led through'the casing 6 and its inner end lies in the bottom of the intake pipe 5. Here it is contemplated that the pipe 23' always will be open to the suction line. Normally, however. this pipe will be submerged in water. It is made relatively small say, for example, a one inch pipe. and consequently, the volume of Water which can be carried off through it is relatively small. However, if the flow of water becomes excessively small with the consequent tendency to reduce the vacuum, the end of the pipe 23 then will be more or less open, thus permitting a relatively large iiow of air through the pipe (since it will conduct a larger volume of air than water at a given vacuum) with a resultant increase in the degree of vacuum maintained in the casing Gf. By making this pipe with an angularly disposed tip as shown at d in Fig. 1, its intake end can be adjusted to diierent levels. Thus the control of the flow of air, water, or mixtures of these fluids through the pipe, which is afforded by the relation of said intake end to the water level in the casing, can be changed to suit different conditions.

For the purpose of taking care of an emergency rise in vacuum which might lock the wire or produce an excessive drag on it, I prefer to connect to this box a vacuum relief valve such, for example, as that shown at 26 in Figs. 1 and 2. This valve comprises a casing provided with air inlet ports 21 and also includes a valve plunger 28 and a spring 29 acting on said plunger and tending to hold it in contact vwith a yielding stop 30. When against said stop it cooperates with a circular seat 3| to prevent any substantial flow of air from the ports 21 into the interior of the valve. The outer surface of the valve, however. is constantly subjected to atmospheric pressure. and the effect of this pressure on the plunger 28 is opposed by such fluid pressure as there may be inside the valve chamber, plus that of the spring 29. Normally this valve plunger simply floats between these two pressures and is moving almost constantly when in operation, although the range of such movement usually is relatively small. If, however, the vacuum rises beyond a normal operating value, the valve plunger 28 will descend suiliciently to admit air into the interior thereof and thence into the box 2 through pipe connections 32 therewith, thus relieving the vacuum. These pipe connections shouldV be made very short so that the effect of change of vacuum in the box is felt as promptly as possible by the valve plunger 28. Such connections,'however, should open into the box 2 at such a point that it will communicate with the interior of the box regardless of the adjustment of the heads but preferably, also, at a point remote from the discharge end 5. The pressure at which this valve will respond can be adjusted either by screwing the casing 26 up or down on its supporting nipple 'it more or less.

33, or by connecting it with the box through an ordinary valve 34 so that this valve can be adjusted by hand to throttle the fiow of air through This valve 26 is utilized chiefly to relieve excessive rises in vacuum and to prevent the locking of the wire which might occur under unusual conditions were such a valve not present.

A more elcientform of vacuum header and associated parts is illustrated in Figs. 4 andl 5. Here the header-or casing 36 corresponds, in general, to that shown at 6 in Fig. 1 and is connected in essentially the same manner through the pipes and valve I5 with the vacuum box. This header or casing 36 is divided by a longitudinal partition d, and by baffles e, f, 9, h and y into six compartments, as will be evident from an inspection of Fig. 5, arranged in a U-shaped series, the partition d compelling the water to flow successively over the partitions f, g and e before it can reach the compartments at the back of the partition where it can then iiow successively over the baiiles h and 7'. It should be understood,

' however, that each compartment must be filled before the water can iiow into the next succeeding compartment. Drop leg sections extend therefore would tend to conduct water to the exclusion of air. Such a vortex is very valuable in making each leg discharge its proper proportion of air therefore under conditions such that this result would not be produced. It also has been clearly established that by belling out the lower ends of the tubes so that they are approximately the same diameter as the respective sections of the drop legs with which they cooperate, the level of water is maintained fairly constant at a point only slightly above the lower ends of these tubes. 'This also is a condition which contributes very materially to enabling the sections to continue their air discharging functions even when their upper ends are submerged. By

mounting the tubes in some such manner as that shown, they may readily be adjusted to the position best adapted to produce the desired results.

downwardly from the respective compartments,

cated. Their lower ends may extend into an overflow box like that shown in Fig. 1, or they may be arranged in any other equivalent manner.

When the volume of water discharged by the box increases sufficiently to submerge the first baffle f to any substantial degree, there is often a tendency for the first section A to fill almost solidly with water and consequently to carry away relatively little air, the air discharging function being performed chieflyby the second section. If the volume of water increases further, the first two sections may discharge relatively little air, most ofthe air being handled by a succeeding section which is only partly filled with water. I havefound that this tendency can be effectually overcome by limiting the working head of water at the top of each section. For this purpose tubes, such as those shown at 31, are positioned directly over each water discharging pipe where their lower ends are in the respective compartments and therefore are always in the stream discharged by the respective sections, while the upper ends of the tubes are open to the atmosphere above the maximum level of water in the casing. Each tube may be conveniently supported by cast-ing a spider,'such as that shown at 38, Fig. 4, into its .upper end, and

making this spider integral with, or securely fasends of the leg sections form portions of, or continuations of, these sections, and the tubes 31 extending into them conduct air to a point Where it is entrained by the water or is trapped in it in such a manner that lit is carried through the pipe and discharged into the overflow box 8 or'y its equivalent. Here again, the exact action which occurs is somewhat obscure, notwithstanding the fact that the results obtained are clearly es- The starting of the apparatus is facilitated in a manner similar to that shown in Fig. 1 by connecting the casing 36 either to an outside source of vacuum or to a supply of water which will serve to prime the drop leg. Such connections may be made by means of the pipe line 43-44, a hand valve 4,5 preferably being included in the latter pipe. In the particular arrangement shown an automatic valve 46 also is connected into this pipe line. It includes a balanced valve plunger 41 connected at its upper end to a diaphragm 48, and at an intermediate point lto a weight actuated lever which tends to hold the valve plunger 41 open. The chamber in the valve casing above the diaphragm 48 is in communication through the pipe 5I with the pressure conditions in the upper part of the header 36. Consequently, the vacuum maintained in this header normally will operate to hold the valve 41 closed. In starting, however, when there is no vacuum inthe header,l the valve 46 will be held open by the vweight 50, thus either admitting priming water to the casing, or else connecting the casing with some other source of vacuum. After the drop leg has created a sufficient degree of vacuum for operating purposes, the diaphragm 48 will be operated to close the valve 41 and it will remain closed so long as the Vacuum maintained in the I header 36 is greater than a value predetermined Y invention does maintain automatically those tablished. It is clear .that the tubes perform a valuable function in creating and maintaining a vortex when the sections are submerged and vacuumA conditions suited to changes in the condition of the web and that it performs this opera-tion far moreeffectually than could be done by amachine te'rder for the reason that it feels the conditions requiring adjustment more quickly than he could detect them, and, simultaneously with feeling them, makes the necessary adjustment itself. The fact that it performs these functions is best evidenced by the stability of the water line under conditions which it is known would shift the water line up or down the wire when the usual vacuum producing mechanisms are employed. In a large measure this unquestionably is due to the sectional water leg and the parts immediately associated with it, but the automatic valve I5l also is an important contributing factor to this result. The invention makes it entirely feasible to use a drop Yleg for creating 4the working vacuum and thus effects an important saving in power, in addition to maintaining vacuum conditions better suited to' changes A Vacuunl gage in the character of the sheet than those heretofore produced with pumps.

rIhe drawings show a single water box only but 'it will be understood that the other water boxes used in a given machine may be similarly equipped.

While I have herein shown and described typical embodiments of myinvention, it will be evident that the invention may be embodied in other forms Without departing from the spirit or scope thereof. Also, while I have given above the best explanation of the action of the apparatus which I am able to make at this time, I do not wish to be limited to this or to any other theory' of operation.

This invention is a continuation, in part, of my copending application Serial No. 141,104, led May 6, i937. The claims of this application are confined to subject matter not disclosed in applicants earlier case just mentioned.

Having thus described my invention, what I desire to claim as new is:

i. That improvement in methods of controlling the operation of a vacuum box in a paper making machine, which consists in causing the between said leg and said box, and meansl tending to close said valve and yieldingly opposing tion of a water box positioned in water extractwater extracted by the box from the web of paper being made to create a working vacuum in said box of an intensity depending chiey upon lthe character of said web and the volume of' water so extracted, and constantly maintaining a yielding throttling action on the discharge of water from the box.

2. That improvement in methods of controlling the operation of a vacuum box in a paper making machine, which consists in causing the water extracted by the "box from the web of paper being made to create a working vacuum n said box of an intensity depending chiefly upon the character of said web and the volume of water so extracted, and constantly restricting the ow of air and water from said box to a degree varying with the character of the web,

3. That improvement in methods of controlling the operation of a vacuum box in a paper making machine, which consists in causing the water extracted by the box from the web ofA paper being made to create a working vacuum in said box of an intensity depending chiey upon the character of said web and the volume of water so extracted, and constantly maintaining a yielding restricting action on the ow of water from said box varying with the rate of discharge of water from the box.

In a paper making machine, `the combination of a. water box positioned in water extract- P ing relationship to the web of paper being made, a drop leg connected with said box and serving to carry the water away from it, iiquid sealing means at the lower end of said leg to cause the water owing therethrough to create a working vacuum in said box, a valve in the connections ing relationship to the web of paper being made, a drop leg connected with said box and serving to carry the water away from it, liquid sealing means at the lower end of said leg to cause the water flowing therethrough to create aworking vacuum in said box, a valve in the connections between said box and said leg where it is subjected to the fluid pressure conditions in said connections tending to open said valve, and adjustable means acting on said valve to yieldingly counter-balance said fluid pressure.

6. In a paper making machine according to claim 4, a construction in which said drop leg consists of a plurality of conduits so arranged that the number of them utilized to carry the water away from said box will automatically vary in accordance with changes in the volume of water discharged by the box.

7. In a paper making machine, the combination with a vacuum box over which the web of paper being made runs in `water extracting relationship thereto, of a vacuum casing communieating with said box and into which the water extracted by the box is delivered, a drop leg leading downwardly from said casing, means for sealing the lower end of said drop leg, said leg being composed of a plurality of conduits coinmunicating with said casing and so arranged that the number ofI them utilized at any time to carry the water away from said box will automatically Vary in accordance with changes in the volume of water' discharged by the box, one or more of said conduits being provided with a tube serving to conduct air from said chamber into the water owing through its respective conduit.

8. In a paper making machine, the combination with a vacuum box over which the web of paper being made runs in water extracting relationship thereto, of a vacuum casing communicating with said box and into which the water extracted by the box is delivered, a drop leg leading downwardly from said casing, means for sealing the lower end of said drop leg, said leg being composed of a plurality of conduits so arranged that the number of them utilized at any time to carry the water away from said box will automatically vary in accordance with changes in the volume of water discharged by the box,

ERNEST Polman.

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