US2244864A - Indicator and control, particularly for paper machines - Google Patents

Description

June' 10, 1941. G, s, wlTHAM, JR 2,244,864

' INDIVCATOKAND ooNTRoL, PARTICULARLY Fon PAPER MACHINES Filed Aug. 25. 1937 'Jnentor vGeorcge SM' qmJr.

attorney Patented June 10, 1941 UN-l'reo STATES PATENT OFFICE y mnlca'roa AND jill-igen; ran'rrcmam I n ron raras. mcmnss George stanford witham, Jr., Portland, om.

appuiera@ Amm z5, 1937, sex-a1 No. mossi s `climi.. (ci. ss-izs) In the manufacture of paper, maintenance and control of the proper moisture content at each stage'of the webs progress is necessary to produce a product. of a desired and uniform quality. It is recognized to be of extreme importance that the moisture content of the finished web be c'orrect, and that the webrcontain neither too much nor too little moisture. Various attempts have been made heretofore to indicate, preparatory to regulating, or to regulate, the amount of moisture in the finished web; but never with entire success.` The plan now most generally used comprises the application toopposite surfaces of the web, or to spa'ced points thereof, of termi*- nals incorporated in a h igh frequency electrical circuit, and since the conductivityof the paper web to such `current varies in accordance with theJ moisture content, such devices furnish an` automatically or through the conscious action 'of one observing the need for correction.

indication of the moisture content, but this indi'- 4 cation is an imperfectone; it is rendered inaccuaccurate indication; furthermore, such devices can only be applied to small areas, and'therefore A they indicate only the conditions which obtain in the regionof these'areas, and it is found in practice that they are'A not a fair indication of the moisture content of the entire web.

I-have discovered that the width of the web, as

it leaves the driersection, or the caIenderstack, or indeed, at any point in its progress, is a direct index of the moisture content of the web, 4regardless of the character of the paper, ofthequality 'of the flbercontent'of the paper, and like considerations., In other words, the width case, to provide 'means which may be operable Y The above indicates a specific application 'ofl this invention in a eld ,where such means are and have been long desired. However, it is also of advantage to apply `the same principles in other fields. For instance, in the shrinking of textilesit is of importance to indicate correctly, and to initiate corrective measures to govern, the shrinkage of the cloth. In a printing press, or in' any reeling or unreeling operation, shrinkage may be measured as an indication of moisture content, and accurate knowledge thereof .permits adjustments to be made to improve the quality of the printed product. In the rolling of metal plates, or sheets, the width vof the sheet is an index of its thickness, and to pro'vide accurate means to measure variations in the width of the sheet or plate,`is to provide accurate means to4 determine the thickness of the plate. In consequence, it is an object of this invention, more generically considered, to provide a means for accurately determining the width of the web (including in this term, any sheet, plate or web-like element), particularly a traveling web, and where its width varies in direct relation to some other characteristic, as moisture content or thickness, to provide means for indicating, through indicationsof the ,variation in width, the variations' in this related characteristic, and as in the former automatically, if desired, to correct anydeparture I shrinks by a given degree with the removal of a f given percentage of moisture, and Athis shrinkage can be accurately measuredand it can be em*- ployed as a direct ,index of the moisture content.

It is therefore, a principal object of my invention, as applied to the manufacture of paper, to give an indication,l more accuratelythan by any means or method heretofore known,` of the moisture content of the web, or alternatively, to operate corrective devices by and in accordance with changes induced by variations in the width of' the web. In this connection it may be noted that 'inv the observed characteristic' from a desired normal. y

As .has heretofore been suggested, and as will become apparent hereafter, the indication or measurement of the width of a traveling web arises as a result of variation in the position of, an edge of the web, to dispose that edge, transversely of the direction of movement of the web, to one side or the other of a normal or desired position. As will be further apparent hereafter, such variation of the' position of the edge from a normal position may be made to operate auto-` matically certain corrective agents. Since these corrective agents may vary widely in form and lin effect, it follows that departure of the edge of use of to maintain alignment of the web at any point in its travel, or for any purpose-for instance, in rerolling, or in feeding the web to a press. In consequence, it is a further o bject oi` i this invention to provide a means suitable to preserve edge-alignment or a traveling web or the While the principles of this invention .may he incorporated in various forms, it is one of the objects 'of the invention to provide such mechanism which may be operated simply and conveniently through the medium of producing e. differential pressure between the interior of s hollow body and the atmosphere in which the web is running; which di'erential pressure is variable by variations in the width of the web as it travels past a slit, at opposite sides ot' which the diierential is applied, thereby making possible the 'measurement ci such variations in the pressure dierentiai to indicate accurately and directly variations in the width o the web,-

though these be small in amount; or if it is variations in some other characteristic, dependent upon variations in the width, that is the thing to h 'uns .in pressure differential, te characteristic .to be s or at' some stages of can not be contacted elers, and to avoid any the web, it is preferable ve any physical contact tiring devices. it is e such ieelers which,

ment which will indicate the change in moisture content between one point and another in the path of -travel ot' such a web.

y Additional objects will become apparent as this specification )progresses` My invention, then, comprises the novel apparatus, both generically and specically. as dis closed diagrammatically in the accompanying drawing, and as will be more particularly disclosed in this speclcation and dened by the claims which will terminate the same.

The accompanying drawing illustrates apparatus suitable to carry out my invention, and

vsuitable for incorporation in paper making machinery, to indicate or to correct for variations in the moisture contento! the web. The drawing is purely diagrammatical in character.

Figure 1 is, in general, a side elevation of the drier section and calender stack of a paper malsing machine, illustrating),r my invention applied thereto.

Figure 2 is, in general, a plan view of the web with the feelers or contact members applied thereto, and illustrating diagrammatically certain indicating and correcting devices.

Figure 3 is a plan view of such a feeler or contact device, and Figure i is a. cross-section therethrough. showing its relationship to the web.

'Ihe last press rolls of a paper making machine are indicated at l9, from whence the paper .web W passes to the drier section 8 and thence to the calender stack 1 to be wound uponl a. reel R. The drying rolls Il are heated by suitable means. such means being customarily steam pipes 82 leading from a main I3. The temperature o! the drying rolls 8| is controlled by regulating the` v:menace sure regulating valve is shown as representative of means to control the steam pressure and hence the temperature of the drying rolls. Since these elements are all common in the art, and form part of the paper machine, with which my invention is not directly concerned, no further description in detail is believed to be necessary.

As pointed out above, I have discovered that the width of the web varies in direct ratio to its moisture content; The edges of the web, when formed, are a precise and known distance apart, l

and as the web is dried, these edges approach one another, and the more moisture is eliminated, the closer they approach. There is a point of approach or spacing of the edges of the web at each point in its travel, which for any given web is the desired normal spacing, corresponding to the desired proper and normal moisture content for thatvparticular weh at that particular point; and this is true regardless of the weight or thickness oi the paper, the chau-actero its fiber, or any other characteristic ci the weh. Accordingly, eelers are provided to contact the opposite edges of the web, or, one Aedge being guided for movement inA a. given path, to contact the opposite edge of the web and to determinel the spacing from the nxeci path oi the opposite edge; if, then, the edge oi the weh is inside of such a feeler, or inside of the ieelere position for normal width and normal moisturecontent,

toc much moisture has been eliminated, and steps should be taken, manually, or automatically, to lessen the temperature o the drying rolls. to regulate the quality of the stock, or regulate the atmospheric condition oi the surrounding air. If, on the other hand, the edge oi the web is determined by the feeler to he outward of this normal position, not enough moisture has been eliminated from the web, and steps must be taken to increase the temperature of the drying rolls, or reversely to regulate the other factors street; ing moisture content of the web. Regulation of the temperature of the drying rolls is an obvious (and generally eective) way of controlling the moisture content of the paper web, but by no means is it the only way, nor necessarily the sole or the only way in which moisture control will be effected. Other ways have been suggested above, and any of these ways, or indeed any 4suitable way, may be employed, as necessity or experience requires or suggests. However, ipsofar as this specification is concerned, where regulation of temperature ot the drying rolls is mentioned, this is intended to include, as an equivalent, the regulationY of any such Hector as suggested above. y

'Obviously it is impracticable to contact the edge of the web with a ieeler pressing inwardly in the plane of the weh. Especially is this impracticable when. as in some cases, it is desirable not only to measure the width ci the web (as an index ot its moisture content) as it leaves the drier section or the calender-stach, but also to measure the width oi the web tor e similar purpose, or for comparative purposes, as it enters the drier section, or evenwhile it is inthe papermaking section. Accordingly,-the feelers are in eiect elements which are placed beneath the'edg'e of the web, but not necessarily in contact with the surface of the web,to be covered more or less by the web as the-web 'varies in width. In using the word beneath" ll do not intend to imply that the teeleris below the web-only'tlint the ieeler, whether above or below the "'wb'is beneath it to the'extent that the web in part.

at least, covers the feeler, and is the more uncovered by the web as the latter is of less width, or as its covering edge shifts inwardly relatiye to the feeler. The feelers are sensitive toV such .covering or uncovering by the web, or alternatively, they aifect some other instrument which is sensitive to the covering A,or Vuncovering of the feeler, thereby generating a forcethe amount a photo-electric cell, or it may be a target upon which such .a cell is directed. The feeler may project a medium, in this instance light, or may be the target for a projected medium such as alight ray; or the feeler m'ay take the form of a device to enable the creation o f a pressure difierential on opposite sides of a narrow slit or other opening extending transversely of the web, which slit, by reason of itsl being covered to a greater or lesser degree, eifects. variationsin the pressure dierential at theopposite sides of the slit, and this in turn will operate indicating or automatic correcting devices. .It is immaterial whether the pressure dierential be created by a higher'external pressure acting upon the web and inwardly through the slit, or acting from the slit outward upon the web.

Thus, as is best shown in Figures 2, 3, and 4 the feelei' I may take the form of a small tube constituting a chamber lll within which a pressure may be created by suitable means, which pressure is permitted to escape through a narrow slit or other small opening shown at il, and extendinggenerally transversely of the edge of the web,

and just beneath an edge of the web and in contact with the surface ot the web. Pressure is supplied, for instance, by a line 2 past regulating means indicated at 20, which will 'produce in the line 2 a constant pressure, and past an orifice 29 the capacity of which is equal t the total capacity of the slit or slits supplied by this line. The pressure in the line 2 affects a pressure sensitive element such as the Sylphon bellows 2l, and by its action upon an arm 22 therehmay be indicated, upon a chart or drum 2l, any variation in the pressure in the line 2. 'I'he slit ll is very uncover the slot .il to a greater degree: thus the pressure can escape. or if it hasbeen permitted partly to escape,` it will escape with greater facil-- ity, with -the result that pressure within the chamber l'is lowered. 'I'his lowering of the pressure is immediately communicated tothe --sy1pnon 2|, and to cream z2, and indicated upon thedrum 22, with the result, it the' device is to be manually controlled, that measures are taken by the 'attendant to decrease the temperature of-.the dryingrolls by reducing the pressure of steam therein. If an automatic control is desired, there may be mounted upon the arm 22 a suitable contact 24 which will engage with spaced contacts 25 and 28, in circuit with an electrically energized control device 28 operatively` connected to the steam valve 80 to move fthe latvter in a direction to compensate for the greater or lesser moisture content which is found in the Aweb at the point A. Alternatively, as indicated earlier in this specification, the manual or the automaticcontrol may effect variations in the character of the raw material, intheatmospheric condition in the conversion room, in the mechanics o f conversion, or in any material or condition airecting moisture content. The arrangement shown and described is purely illustrative and rather primitive in character, and any suitable control maybe employed, it being the purpose only to indicate how, through the medium of variations in the width of the web due to variations in the moisture content thereof, suitable indications can be given and corrections autonarrow,.say .007 or .008 inch, and ofl'ers considerable resistance to relief of pressure through it,

and the more of its length iscovered, the greater is this resistance. If it is fully covered the resistance is 'the maximum permitted by the con, stant pressure device 2l; if it is fully uncovered the pressure medium escapes from the slit as fast as it passes the orifice 29, and there is no pressure in the line beyond this oriiice.V

It will be evident that since the slot l I is nearly or substantially wholly covered by the edge of the web when the latterisof normal width, correfeeler, located at the point A, preferably betweenA thecalenderstack1andtheheelR.willbe acted upon by tbe consequently narrower web to maticallyr made; or the condition may be simultaneously vand automatically corrected for and indicated to an attendant,

Preferably at the point A two such feelers l are provided at opposite edges of the web, and

in this case if one edge of the web is not guided to run precisely in atrue path, without variation to one side or other of that path, the indication -wll still be correct inasmuch as the pressure within each chamber I0 .will be the aggrega of the pressure as it is affected by the total length oi' the slits Il in the two feelers l at opposite edges of the web.' If -the edges of the web shift to one side or the other, without any change in the width of` the web itself, while one slit will be opened a greater amount the slit in the opposite feeler will be closed by the same amount and the aggregate pressure in the interconnected feelers will be identical, and in consequence, there`v will be no adjustment and no change vin the indication. If, however. there is a change in the width of the web, the combined length of the slits in the two feelers will change, .and suitable indications will appear and correction be made.

. It is preferable also in some instances to provide a feeler or feelers at/the point B or near in the passage of the web through the drier. section.y There may be .provided an indicator 23 to indicate the width of the web at the point B or to indicate any changes in its'width at that point. This indicator 2l is, or may be in all respects analogous to that shown at 22. but isr` connected to the line 2 past individual constant Y pressure and orifice controls, separate from those anuncia It may be`desirable to accommodate the niachine to webs of dierent width, or because oi varying temperature conditions or other conditions, to eect adjustment ofthe eeler l inwardand outward of the edge or the web. To this end, each such feeler, or at least one of each pair at the opposite edges of the web, is mounted in a support i2 which is fixed in position, and which carries a screw i3, engageable with a threaded lug ou the tube i, whereby1 by a tine adjustment the tube may be moved inwardly or outwardly of the edge of the web.

Since the tube is thus adjustable, it is' necessary to provide for the connection of the pressure line 2 through nexible connections or the like, as

' indicated at l in Figure 3.

. While heretoiore the feeier i has been described as a single slitted tube, disposed only along or beneath one surface oi' the web, this description has been purely for simplicity of understanding. Such s. single ieeler-will operate, and by itself is within the scope of my invention, but for most satisfactory operation it is preferred that it be constituted as two such slitted tubes, one at one surface or the web and one directly opposite at the other surface of the web, and both connected to a common pressure line through a constant pressure device 2B and oriiice 2d common to the two feelers. The arrangement is shown in Figure Ai.

Thus arranged, pressure from one (designated for convenience the iower one) tends to lift the web; substantially equal pressure from the other (designated, to distinguish it, the upper one),

directed immediately towards and opposing the pressure from the lower feeler, tends to press down the web. As a result, the web tends to oat midway between the upper and lower feelers, but

to contact neither. iii the webs edge moves inwardly, both the upper and lower feelers havev their slits uncovered by the same amount, and being connected in parallel to the same constant pressure and constant volume devices 20 and 29,

' the reduction in pressure within their chambers -as an indication oi the lesser thickness. if the web exceeds the maximum desired thickness, the interruption o the iets( is graeter, or may be total, and the increased vpressure indicates the greater thickness. l

it will now be evident that the line 2, instead of supplying pressure to the interior chamber llo of the members l, might insteadproduce a reduced pressure within that chamber, so that the medium, air, is projected through the slit il from the open atmosphere into the interior. It will .be further evident that the vrnember l might also be formed as the target of a photo-electric cell, or might be the cell itself, so that the strength or the current is a iunction oi the amount of coverage Aci the member i, which of course is dependent upon the position of th? edge oi the web.

Zity will also be evident that the invention is -applicable with equal facility to the measurenient of the width of any'web: for instance. in the shrinking of textiles, as previously mentioned, or in the rolling of plates and sheets. Since, inthe latter instance, the width of the plate or sheet is a function of its thickness, a similar arrangement to that described may be provided to measure, and ii desired, to correct the thickness of the plate or sheet in accordance with variations in its `width which are a direct result of variations in its thickness. The invention, therefore, generically considered, is a device and a method for measuring and indicating (including -ilie conception of correcting) variations in the position of an edge of or in the width of a web, usually a traveling web, and for indicating variations. in characteristics such 'as moisture content, thickness, character or material or workmanship, atmospheric conditions in the conversion room, in the mechanics of conversion, in the adjustment of the machine itself, or in of the many characteristics or conditions which aectan'd which are a direct function or criterion of variations in the width of the web.

What I claim as my invention is:

l. Means to determine the width of a traveling web,7 comprising two interconnected hollow members, disposed beneath but substantially out of contact with opposite edges of the web, and each having a small slit extending transversely of the adjacent edge of the web, in position to be masked more or less in accordance with variations in the width of the web, means to create a pressure differential, through the slits, between the interior of said members and the atmosphere, which pressure diierentiai will vary in amount fin. accordance with the aggregate amount of through their slits, which pressure dierence will vary in amount in accordance with the aggregate amount of masking ci the slits by the dispiacernent of the edge o the web. as the web varies in width, and indicating means responsive-to such changes in the pressure difference.

3. Means to denlnine the width oi a troveiing Web or the like, comprising two interconnected hollow members, disposed beneath oppo@ site edges of the web and each having a, smali slit extending transverselr1 ci the adjacent edge of the web, in position to be mashed more or less, in accordance with variations in the width of the web, means to adjustA one such member, relative to the other, transverse-lr of the web, means to create a pressure diderence between `the atmosphere and the connected interior of said members, through their slits, which pressure diierence will vary in amount in accordance with the aggregate amount of masking of the slits by the opposite edges of the web, and indicating means responsive to such changes in the pressure difference'.

GEORGE STANFGRD WITHAM, 3s.

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