US1714846A - Method and apparatus for steering belts - Google Patents

Description

5 Sheets-Sheet l zvevz 0? May 28, 1929. J. G. CALLAN METHOD AND APPARATUS FOR STEERING BELTS Original Filed May 15. 1922 May 28, 1929.

. 1. G. CALLAN METHOD AND APPARATUS FOR STEERING BELTS 5 Sheets-Sheet Original Filed May 15. 1922 May 28, 1929. J. a. CALLAN METHOD AND APPARATUS FOR STEERING BELTS Original Filed May 15. 1922 5 Sheets-Sheet May 28, 1929. J. G. CALLAN I METHOD AND APPARATUS FOR STEERING BELTS Original Filed May 15. 1922 5 Sheet-Sheet Eat/e g??? z a May 28, 1929. J. G. CALLAN METHOD AND APPARATUS FOR STEERING BELTS Original Filed May 15. 1922 5 Sheets-Sheet 5 Patented May 28, 1929. i

Jenn GURNEY CALLAN, or cameraman, I p

MANurAorunrne COMPANY, or BOSTQN, iaassncnusnr'rs, a CORPORATION 0r- MA SSACHUSETTS. 4

Fianna ranssecnusnrrs, nssrenon To EASTERN METHOD AND APPARATUS FOR STEERING BELTS.

Application filed May 15, 1922, Serial No. 561,140. Renewed April 15, 1929.

This invention relates to the method and apparatus for guiding belts into the nip between a pair of cooperating pressure rolls. More specifically it has application to the guiding of continuous belts of multiply textile fabric through the'nip between a pair of calender or similar rolls, preferably one hard and the other softer, pressed heavily together in a machine for imparting a fabriclike surface to paper. The method, however, is 0t general application Wherever a belt or web is to be guided in a nip between rolls or their equivalent.

The art of guiding flat belts on to cylin-e drical pulleys is well known. When it is desired to ca use a belt to shift along the pulley face it is urged edge vise at a point somewhat ahead or that where it makes its ongoing contact. with the pulley, an action which guides the belt by changing the approach from a normal to a slightly angular one and which incidentally involves a loosening of the wrap of the belt around the pulley on the edge toward which traverse takes place.

Where the belt is guided into a nip between rolls instead of on to a single pulley or drum, the action involved in guiding or steering the belt diil'ers radically from this well known action just outlined, and previous attempts to guide belts into nips have had erratic and unexpected results on account of being based on this apparent analogy which turns out not to be a true one. The conditions are in fact as follows.

Subject to small correction factors, the perhpheral speed of the rolls at any point along the nip precisely determines and measures the rate at which the belt is fed through at that pointsince the pressure exerted by the rolls upon the belt fartoo great to allow any slhaping in the ordinary sense of the word. It now all the conditions are ideal, the belt feeds through at the same speed at all points of its breadth and maintains its proper lateral position and does not wrinkle as it goes into the nip. These ideal conditionsare principally the following: (1) therolls true cylinders with parallel axes under equal pres sure at both ends; (2) the longitudinal center line or axis of the belt initially at right angles with the line of contact between the rolls, that is, with the nip; 3) the belt, which is joined into an endless form, of exactly the same length at both edges and also on all other intermediate lines measured parallel to the edges. I 1 a i If any of these conditions be not exactly fulfilled as usually happens ilIPIdClllCQythGl] without-the intervention of a suitable. guiding or steering device the belt fails to run true in one or the other lateral direction as will be seen from the following.

If the belt does not feed in squarely, tha is, it its longitudinal edge or axis is not/at right angles with the line of contact between the rolls, then obviously the belt will edge over toward one side,since theinstantaneous direction of travel in any case is at right angles to the line of the nip. It the rolls are of greater diameter at one end than at the other, the end of greater diameter measures off and feeds forward a greater length of belt per revolution than the end of lesser diameter and the belt will thus gradually be thrown to a position where its longitudinal axis is no longer at right angles to the line of the nip and where it therefore edges over to one side.

If the axes of the rolls are not parallel their contact would theoretically be a point and not a line and actually with roll fiexure and distortion is a warped line instead of a straight line. Theefi ect on the feed of the belt depends on the degree of an'gularity, the

relative position of the two rolls, and the relative hardness of the roll materials and; may be erratic if the departuretrom parallelism is appreciable.

It the pressure at one end be materially greater than at the other, then with the heavy pressures actually used in the machine the difference in longitudinal elastic extension of the two edges of the belt, momentarily coinpressed as it passes through the nip, and the difference of radius of the two ends of the softer of the pair of rolls, produces a din erence in the net rate of feedat the two edges measured on the uncompressed belt. This will gradually throw the belt out of proper position.

If the belt is notof exactly the same length on the two ed es, the action may be illustrated by an example. Suppose the belt to be thirty feet long on one edge and the other edge to be thirty feet plus onetenth of an inch. N ow when the rolls have run until their circumferential travel has been thirty feet,

i the first-named edge will have returned to its traveled three hundred feet one edge will be an inch ahead of the other and the belt will be feeding into the nip at an angle sufficient to cause rapid edging over to one side.

Difference in length of the two edges of the belt is common in practiceand is the most in'iportant cause of failure to run straight; the other departures from perfection are usually found in some degree and the expected consequent tendency of the belt to travel over to one or the other side does actually develop. Furthermore, if without any other added procedure the belt is swung bodily back where its center line again squares with the line of the nip (as would be done if it were feeding on to a pulley) or if itis prevented from'leaving there, then the inequality of feed on the two edges causes a looseness or pucker on the edge feeding in slowest, the rolls refuse to take up this slack, and it eventually forms a wrinkle which passes through the heavily weighted nip and the belt is at once cut diagonally in two and destroyed. Many such failures of direct steering were followed in my experiments by various modifications some of which guided the belt if all ideal conditions were very closely met. Comparison of common factors ofthe partial successes led to the present method, which is wholly successful under commercial conditions.

The belt is put under comparatively heavy, but not destructive, initial tension, and the guiding or steering is accomplished by use of some means or mechanism that stretches one edge more than the other within the elastic limit of the material. The edge that receives the greater tension is lengthened the more and therefore progressively falls behind as the belt is measured off and fed forward by the revolution of the tightly engaged pair of rolls. This progressively corrects the angle of entry of the belt to the nip and causes it to edge over away from that side that is under the most tension. This is the essential guiding and steering method and it can be carried out in a number of ways, some of which have particular advantages. The method will be described later in further detail and afterward a preferred embodiment will be disclosed.

With regard to the initial tension it is clear that not only must the two edges of the belt keep exact pace with each other, but any and all elements parallel to the edges must keep the same step or the surface will fall into irregular wrinkles and be cut to pieces by the pressure. The initial tension may be applied by a head roll which acts to even out local irregularities of length and is a principal means of accomplishing this action, both momentarily and permanently, the latter durmg the early running of a new belt when it is receiving soniepernianent stretch as a re-' Figure 2 is a plan of a steering mechanism.

Figure 3 is a side elevation of the same mechanism.

Figure t is an end elevation of the same mechanism.

Figure 5 is a section on line 5 ure 2.

' Figure 6 is a fragmentary section on line 66 of Figure 2.

Figure 7 is a top plan of one end of the machine. 1 v i Figures 8 and 9 are diagrammatic views illustrating two methods preferably used in conjunction by which steering may be offected.

Referring to Figures 1 and 7, at 1 are indicated a pair of spaced parallel side frames, each provided with a vertical guideway 2 to slidably receive journal blocks 3, 4., and 5 of calendering or similar superposed rolls 6, 7, and 8. The lowest roll 6 and the top roll 8 are preferably formed of steel so as to be comparatively hard, while the intermediate roll 7 is formed of relatively soft material such as highly compressed cot-ton, A heavy pressure is exerted to press these rolls together, as shown, this being effected independently at 5 of Figeach end of the rolls, there being fulcrumed on a pin or pintle 10 fixed in a bracket 11 projecting from one edge of each frame member 1, a lever 12 having a weight 13 at its free end. Near the fulcrum 10 is pivoted the lower end of a link 14, the upper end of each threaded in the hub of a hand wheel 15. Also threaded in the upper end of this hub is a link 16 engaging at its upper end a lever 17 fulcrumed at 18 to a pair of bracketsl.) fixed to the top of the fran'ie 1. The links 14 and 16 are reversely threaded in the hand wheel so that by turning this wheel their ef fective length may be shortened or lengthened as required. Near the fulcrum 18, the lever 17 bears on a post 20 which projects through a guideway in the upper end of the frame 1 and is fast at its lower end in the bearing block 5. The lower bearing block 3 is supported on a bracket 21 fixed in the lower partof the guideway 2. Bythis means the weights 13 acting through multiplied lever arms exert a heavy pressure between the rolls. The rolls 7 and 8 are the calender rolls which cooperate to form a nip through which the belt is to be guided. Pressure ex erted at either end of the roll 8 be adjusted by changing the weights 13. Adjustment of this pressure differentially corrects for slightly conical shapes of rolls and also causes a local elongation of the belt to cause a steering action as above described.

A pair of fabric belts between which the paper to be finished is passed are shown 30 and 31. The upper belt 30 passes through the nip between the rolls 7 and 8, around over the top of the roll 8 and in an upwardly inclined direction over a steering mechanism, indicated generally by S, which will be later described. t then passes in a downwardly inclined direction over a head roll 35, then back and over a guide roll 36 carried by the frame 1 which so posit ned as to cause the belt to engage the roll 8 somewhat in advance of the nip between it and the roll 7. This engagement with the roll 8 serves to smooth out local wrinkles which might otherwise cause trouble when the nip is reached.

The head roll 35 is carried on horizontal ways as all) and is urged away from the colon-- dcr rolls by means of heavy wei hts, such as 41, each weight being fixed to a chain l2 passing over a chain wheel 43 carriedby a shaft a l. A. pair of small drums a5 fixed to this shaft have wound thereon cables t6, the for ward end of each of which is attached to a carriage 47, which is slidable on eachway 40. The carriages 47 on opposite ways maybe connected for simultaneous movement by a crossbar 43. It is desirable that the angular position of the head roll may be adjusted in order to conform somewhat closely to any inequality of lengths of opposite edges of the belt to avoid placing too great a load on the steering mechanism. For this purpose the head roll may be journaled in bearings 50, each individually adjustable on its carriage 47 by means of a screw 51, I

The lower belt 31, passes between the rolls 8 and 7 and then downwardly to a guide roll near the base of the machine, From beneath this guide roll the belt trave s upward ly about the steering device S and around a head roll 56 which may be mounted in the same manner as the roll 35. From the head. roll the belt passes beneath the guide roll 57 positioned somewhat below the horizontal plane of the nip between the rolls 7 and 8, so as to engage the roll 7 in advance of the nip for the same purpose as that described in con nection with the guide roll 36 for the belt 30.

The paper to be calendered is shown as in the form of a roll 60 which is supported at the end of a pair of levers, one of which is shown at '61 in Figure l, the weight of the paper roll being held by a chain or cable 62 passing down over a belt pulley 63 and then upwardly to a winding drum 64, which is normally held from rotation by means of a locking pawl 65. The roll of paper is prevented from rotating too freely by meansof a brake drum 66 fixed to rotate therewith and about which is passed an adjustable brake band 67'. The paper may be supported in an other suitable manner as this forms no part of the pi'esentiinvention. The )a- )er 18 led from the roll 60 us over a i tension roller 68 vertically adgustable in a frame 69 supported from the ways lO. After for compensating approximately for large oifierences in length of edges so that the automatic gear inaynot be overburdened. For

the hand controlled function one edge or the other of the belt is given excess stretch by ad justing the weighted head roll in the manner above described to a slightly angular position. This is not usually necessary, except temporarily with a new and uncommonly irregular belt.

The automatic mechanism, in general, comprises a steering roll, as R, which is shown more in detail in Figures 2 to 5 inclusive, which is pivoted to swing a-bout an axis positioned substantially centrally of its length as shown at 80. The automatic mechanism S,

S that I have found best bears some physical resemblance to the rolls used to steer Fourdrinier wires, felts on ruling machines and the like, difiering particularly therefrom in that it does not act on a substantially flat part of the belt, but is placed in the vertex of an angle formed by the approaching and Need ing stretches of the belt, the angularity of the two stretches being different relative to the plane of swing of the guiding roll, as shown in Figure l, in which the double arrows l and P indicate the plane of swing of the steering rolls which are shown at R, B. This mechanism, if suitably proportioned can be placed at any point in the traverse of the belt Where there is room for 1t, but it works best in the position shown in Figure 1 engaging a part of the belt approaching the head roll and receoing from the calender rolls, the direction of motion of these belts being indicated by the arrows m, m.

The action of this steering mechanism involves two partly independent actions which combine to adjust the position of the belt in the following manner. When the belt becomes displaced from-its desired position it actuates a suitable mechanism such as will be.

later described which swings the steering roll in the plane indicated by the arrows P and P. it will be seen from Figures 1 that the plane of the belt on the stretch approach ing the steering roll is more nearly parallel to of the other end of the roll may stretch its edge less,'or not at all, 01' release tension upon it, according to the exact angular relation between the plane of approach and the plane of swing of the roll. This differential stretching of one edge, which is the edge from which it is desired to guide the belt, is alone suflicient to steer the belt fairly well when ideal conditions are approximated, but with the arrangement of parts shown there is another stretching action which eoincidently stretches the edge of the belt locally just as it enters the nip on the side from which it is desired to steer it. This is as follows.

W hen the steering roll swung as described, it tends to directly displace the belt sidcwise toward that end of the roll that is swung upstream or in a direction opposite to that in which the belt is traveling. This action well understood in connection with steering devices employed to guide Fourdrinier wires, and it more or less displaces the belt in the stated direction on the head roll. This displacement alone in the absence of any COlllpfi-l'ztilVfily heavy initial tension would only throw the belt over to a position where it would present to the nip on the losing edge still more slack which the nip is entirely incapable of taking up and would therefore develop no steering action. vVhere there is sufficient initial tension the following action oc curs. When the belt is thrown to one side of the head roll, as shown in dotted lines in Fi g ure 9 which illustrates the lower port-ion the upper bcltSO between the head roll and the i p, the normal lines of tension parallel. to the center line of the belt are relieved, and there is substituted a main diagonal line of tension, as sh own by the arrow t, extending from the corner at the head roll and at the edge toward which the belt is moved, to the diagonally opposite corner at the nip, this being shown in Figure 9 in a somewhat exaggerated degree. its any given element of the belt passes through this diagonal it is momentarily stretched in a diagonal direction, the longitudinal. component of which'is much greater than the lateral component when the steeriuggear is located as shown in Figure 1. Just as the belt enters the nip this stretch is fairly local at the edge from which it is desired to steer the belt, that is, at the point 0, and the momentary elongation at the in stant of entering the nip has the same eii ect as an equal permanent elongation from direct stretching of the whole edge, namely, to tend to cause that side to fall pri'igressively behind and consequently to tend to steer the belt over to the opposite side. That is the same side tothe more tightly stretched edge being shown at a in Figure 8 and the less stretched edgeat 6, this direct stretch being caused, as before described, by the swinging of the steering roll R to the dotted line position in Figure 8. As inthe case of the direct stretch this diagonal stretch alone will steer the belt when ideal conditions are approx'inated.

It will now be shown why the combination of the two actions is more effective than either alone under probable departures from ideal conditions. lVith the direct stretching action, duo merely to the swinging of the roll in the unsymmetrical gable of the belt passing over or under it, the degree of stretch is greatest at one edge, least at the other, and varies progressively and evenly between, this being shown diagrann'natically by the shaded stress triangle in Figure 8. lVith the diagonal tension due to forcing the initially stretched belt over sidewise on the head roll, the stretch is somewhat localized at and near one edge, and drops at first rapidly and afterward more slowly at points progressively approaching the other edge, this being indicated in the shaded stress diagram in Figure 9. Now if the belt were of exactly equal lengths at the edges and the inedianportion, then the firstnained symmetrical stretching action would be the one sought, and it could be easily obtaincd by swinging a belt-steering roll contacting with a nearly flat portion of the belt about an axis parallel with the center line of the belt at the place of contact, or by initially taking up slack on the head roll by adjusting it to the proper angular position. The reason thatithe more elaborate method as described is more satisfactory is that the incidents and accidents of operation always lead to a slight additional stretching of the insupported edges of the belt, and a judicious superposi tion of the diagonal pull, which localizes the steering tension at the edge, compensates for this and leads to an extremely satisfactory guiding action which is not fully duplicated by either method alone on commercial belts of common degrees of departure from com- .plete flatness and symmetry. is my theory to the reason for the excellent results actually attained with the empirically determined relation between the two actions that I have found best. I have round that a good action is achieved with a thirty foot belt inakin g a total deflection from plane of from twenty to thirty degrees as it passes over the steering roll, divided so that the belt approaches theiroll in a plane not far from parallel to that in which the roll swings, and recedes the roll. in a plane making a Iroin twenty or thirty degree angle with this plane of swing. il ith these proportions this mechanisni will. ordinarily hold belts ofeasily noticeable edge sag and difference of length on the two edges within half inch of desired location in'the nip throughout-their periods of life. p

An added precaution against the development of puckers and consequent destructive wrinkles at the edges is the use of the guide rolls 36 and '57 which bring the belts into contact with the calender'rolls at a point some distance ahead of the nip as shown in Figure 1 so as to wrap the belts over substa tial arcs of the calender rolls before reaching the nip.

Referring now more particularly to Figures 2 to 5, the steering roll R is journaled at opposite ends in bearings 81 and 82. As shown in Figure 2, thebearing 81 is fixed by a single bolt 83 to a frame member 84 which is pivoted by a pin at to a cross-frame member 85. The bearing 82 is adjustable along a guide block 86 by means of an adjustscrew 87, the block 86 being fastened by a single bolt 88 to the frame 85. By this means the angularity of the roll relative to the frame 84 may be adjusted according to conditions, the bearings swinging about the securing bolts, so as to relieve the automatically adjusting mechanism to be described from the entire adjustment necessary to cause the belt to run true. The cross frame member may be supported in any suitable anner asby mountin it on the guides 40 and maybe made angularly adjustable thereon by any suitable means, if desired, to change the angle of theplane of swing of the roll relative to the gable formed in the belt by this roll. In orderto support the ends of the frame 84, ball casters, as'shown at 90, may be fixed to the lower face of the frame 84 and. bear on wear plates 91 fixed to the cross frame member 85. To oppositeends of the frame 84 are fixed the ends of links 95, the 0pposite ends of which are adj ustably fixed as by means of bolt and slot connections 96 to end plates 97 of steering actuating mechanism indicated generally by 100.

The end plates 97 of this mechanism are carried at the ends of a pair of spaced guide rods 101 on which are slidably mounted adj acen t the end plates brackets 102, while toward their center, the guide rods 101 have fixed thereto a pair of spaced brackets 103 and 104. Journaled at opposite ends in the brackets 103 and 104, as shown in Figures 2 and 3, is a short shaft 105 having its central portion 106 formed as a screw with a coarse pitch. in threaded engagement with this screw is a nut 107 provided with a shank portion 108 depending within the upper end of a vertically extending tube 109 (see Figure 5) which'is fixed at its lower end in a cross frame member 110 of the machine. This construction permits the nut 10'? to oscillate slightly about a vertical aXis but prevents it from other motion. Consequently rotation of the shaft 105 note to move the brackets 103 and 104 laterally carrying the entire mechanism 100 therewith and :through the'lin'ks 95, imparting swinging motion to the roller R about the pivot 80. Turning motion is imparted to the shaft 105 by -means ofa gear fixed thereto meshing with a pinion wire 116 journaled in a bearing 117 extending up ward from the bracfket104 and having its adjacent end slidably keyed to a friction wheel 118 beyond which it is journaled in' a' bearing 119in one of the brackets 102. The opposite end of the pinion Wire 116 is now slidably journaled' in a housing- 120 carried by the opposite bracket 102 and has g-fixed thereto within the housing ab'evel gear'121 meshingwith a bevel pinion 122 carried by a vertical stub shaft 123 whichipinion in turn meshes with a :bevel gear 124 :mounted to retate with a shaft'1'2'5 towhich is fixed a friction wheel 136. Thefriction wheels 118 and 136 are formed with outer'bearing faces "140 with which engage similar smaller mating friction wheels 141 and 142. These Wheels are carried by stub axles 143 and'144 fixed in vertically sliding bearings 145 and 146 and pass when'th'e belt-travels laterally, these wheels being normally so spaced apart as to just clear the beltedges when the belt is in its normal lateral position. Ifthe'belttraVels to one side or the other it engages in one or the other of the notches 155, its longitudinal motion causing rotation of the corresponding friction wheel and imparting rotation in one or the other direction, depending on the friction wheels engaged, to the pinion wire 116, consequently rotating the gear 115andimparting lateral motion to the roll-moving mechanism and consequently swinging the roll in a direction to steer the :belt away from the friction wheels engaged thereby.

This

motion 'ofthe mechanism 100 laterallyis such asto move the friction wheels themselves in the direction of the travel of the belt-which is to be corrected, thus tending, to move the the corrective motion have been sufficient to cause the belt'to move in the opposite direction any ove'rthrowin this directioncauses the belt to contactthe opposite setof friction rolls tocausea return motion of the 'steering roll to prevent over correction, this mechanism friction wheelsout of engagement 'wi-th'the serving as onetype'of follow up" device such as is commonly employed in power-steering mechanisms. 1

It is desirable that the distance between the sets of friction rolls should be adjustable to provide for different widths of belt and also that they should beadjustable as a unit relative to thecalender-rolls so that the normal'lateral position relative theretomay be predetermined. For this purposeone of the brackets .102. hereinshown as the left hand bracket in Figures2 and 3, is provided with a threaded depending lug 160 in which engages the threaded end of a shaft 161. Also threaded on this portion of the shaft 161 is a gear wheel 162. The opposite end of the shaft 161 is oppositely threaded with the same pitch through a lug 163 depending from the opposite bracket 102 while fixed to this shaft is a gear 1640f the same size as gear 162.

-Me'shing with the gear 162, which as before stated, is threaded on the shaft 161, is one endfof'a piece of pinion wire 165 journaled between a pair of forked arms 166 depending fronithe bracket 103, these arms 166 holding the pinion wire in mesh with the gear 164. The opposite. end of the pinion wire extends through one of the end plates 97 in a Ushaped slot 170 of, such size that the wire may be broug'ht'down intoeither of the sides of the slot as 173 and 17 5 and be there retained by an arm 171 (see Figure 4) urged downwardly thereagainst by a spring 17 2; When the pin ion wire rests in side 17 3 of the slot170, it is out of mesh, with the gear164 while when it is. in the opposite side 17 5 of this slot it is inmesh with the gear 164. The outer end of this pinion wire carries an actuating handle 176. If now the pinion wire is engaged in the'side 17 5' and is turned, rotation is imparted to both the gears 162 and 164 in the same direction. Rotation of the gear 162 is effected at the same angular velocity as the rotation of the shaft 161 since the gears 162 and 164 are of the same size. There is therefore no relative motion of the shaft and gear 162' andhence the shaft is longitudinally fixed relative to. the brackets 103 and 104. The lugs 160 and 163 are thus caused to move toward or from each other depending on the directionof rotation of the handle 17 6 since they engage oppositely threaded portions of the shaft. This action thus increases or de creases the spacing of the sets of friction wheels without changing the lateral position of the axis centrally therebetween. In case the pinion wire ismoved'to occupy the slot side 173, it is out of mesh with the gear 164 so that the screw shaft 161 is not revolved when handle 17 6 is turned but the gear 162 is screwed thereon; thus carrying both the brackets 102 together .relative to the bracket 103, the spacing of thesetsof friction wheels not being effected, but, both being moved together laterally to position the belt. ,lVhen the pinion wire is out of meshwith the gear 164, it is desirable that the screw shaft 161 be held from rotation. For this purpose a pawl shown in Figure 6 at 180 may be employed. This consists of a plate engaging at one end over one-of the guide rods 101 having a depressed portion engageable by the pinion wire 165 so as to hold its edge 181 out These friction wheels are preferably covered with friction material such as cork linoleum.

It will be seen from this description that rough preliminary steering adjustments may be effected by hand by adjusting the angular position of the head roll and by applying differential pressure at opposite ends of the nip, and that more accurate final adjustments are effected automatically, as conditions require, by means of the swinging steering roll which acts in two different ways to perform its intended function;

Having thus described an embodiment of this invention it should .beevident to those skilled in; the art that many changes and modifications might be made therein without departing from its spirit orscope as defined by the appended claims. I

Iclaim:

1. The method of guiding a belt into a nip between two rollspressedtogetherunder heavy pressure which comprises run ning the belt under heavyv tension and applying a differential tension to opposite edges of the belt to tend to maintain the belt in a definite lateral position.

2. The method of guiding'a belt into a nip between two rolls pressed together under heavy pressure which comprises running the belt under heavy tension and applying a differential tension. longitudinally of the belt at opposite-edges to tend to maintain the belt in a definite lateral position.

The method of guiding a belt into a nip between two rolls pressed together under heavy pressure which comprises running the belt under heavy tension and imparting a localized edge tension thereto at the nip at one edge to tend to maintain the belt in a definite lateral. position,counteracting any normal tendency for the belt to move laterally. a

4. The method of guiding a belt into a nip between. two rolls pressed together un der heavy pressure which comprises running the belt under heavy tension and imparting a diagonal'tension extending to one edge at said ni p to impart a local stretch of said edge at the nip to tend to maintain the belt in a definite lateral position counteracting any normal tendency of the belt to travel laterally. p

5. The method of guiding a belt into'a nip between two rolls pressed together un der heavy pressure which comprises running the belt under heavy tension and applying a dill ereniial tension longitudinally to opposite edges of the belt, and a diagonal tension extending to one edge of said belt at the nip to tend to maintain the nip at a definite lateral position counteractingany normal tendency of the belt to travel laterally.

The method guiding a belt into a nip between two rolls pressed together un der heavy pressure which comprises running the belt under heavy tension and applying a diilerentialtension longitudinally to opposite edges oi the belt and imparting to the edge more heavily tensioned an additional local tension at said nip to tend to n'iaintain said belt in a definite lateral position.

7. The method of guiding a belt into 21 mp between two rolls pressed to ther under heavy pressure whica comprises running the belt under heavy mine and applying a di llerential tension long tudinally to opposite edges of the belt and imparting a tension diagonal to said belt extendin g to the more heavily tensioned edge the nip to tend to maintain said belt in a definite lateral posi lion.

8. The method of guiding a belt into a.

nip between two rolls pressed together under heavy pressure which com .ses running the belt under heavy tension and applying a dilTerential tension longitudinally to opposite edges of the belt and imparting to the edge more heavily tensioned an addi tional local tension at said nip, said tensions being antoniiatically adjusted to tend to maintain the belt in a definite lateral position.

9. The method of guiding a belt into a nip between two rolls pressed together un der heavy pressure which comprises running the belt under heavy tension and applying a dili'erential tension longitudinally to opposite er of the belt and imparting a tension diagonal to said belt extending to the more heavily tensioned edge at the nip to tend to maintain said belt in a definite latoral position, said tensions being automatical ly adjusted to tend to maintain the belt in a definite lateral position. 7

10. The method of guiding an endless belt passing through the nip between a pair of pressure rolls which comprises differentially adjusting the pressure exerted by said rolls at opposite edges oi said belt to etlect a variable local elongationthereof at the nip.

11. Themeth'od of guiding an endless belt through the nip of a pair of pressure rolls which comprises imparting a differential ten sion to opposite edges of said belt and differ entially adjusting the pressure exerted by said rolls at opposite edges of said belt to ef-,

feet a variable elongation thereof of the nip supplementmg the variable elongatlon due to said tension.

12. The method of guiding an endless belt through the nip of a pair of pressure rolls which comprises automatically imparting a differential longitudinal tension to opposite edgesfot said belt proportionaltoand such I A as to oppose normal tendency to lateral move ment of said belt, and dillerenti'ally adjusting the pressure exerted by said rolls at opposite edges of said belt to ellect a variable elongation thereof at the nip supplementing the variable elongation due to said tension.

13. The method of guiding an endless belt through the 'nip of a pair of pressure rolls which comprises in'iparting a diilerential longitudinal tension to opposite edges of said belt, a tension diagonally across the width of said beltv to the heavier tensioned edge at the nip, and imparting a dii'lerential pressure to said rollson said belt to impart a local elongation thereof at the nip supplementing the elongations due to said tensions.

14-. The method ot'guiding a beltbetween cooperating relatively hard and soft pressure rolls which comprises exerting dillerential pressure on said belt between said rolls whereby the effective measuring diameter of said relatively soft roll isdecreased at the end of greater pressure. V

15. In a machine oi": the class described, a pair of rolls, means for pressing said rolls together under heavy pressure, anendless flat belt passed between said'rolls,.a1'1d steering means for said belt arranged to dillerentially stretch opposite edges of said'belt to tend to maintain the belt in a definite lateral position. i 1 m 16. In a machine of the classdescribecba pair of rolls, means for pressing said rolls together under'heavy pressure, an endlessflat belt passed. between said rolls, and steering means for said belt arranged to difi erentially elongate opposite edges of said belt to tend to maintain the belt in a 'delinte lat-- eral position. j

17 In a machine of the class descril ed, a pair of rolls, means for pressing said rolls together under heavy pressure, an endless flat belt passed between said rolls, steering means for said belt arranged to impart variable differential elongation to opposite edges of said belt, and means for controlling the extent of such elongation automatically. 7

18. In a machine of the class described, a pair of rolls, means for pressing said rolls together under heavy pressure, an endless flat belt passed between said rolls and means acting in a plurality of wayseach controlled tial elongation of o iipositeedges pair of rolls, means for n'ossin between sa by motion of the belt for imparting a difleren of said belt at the nip off said rolls. I

19. In a machine of the class described, a pair oil? rolls means for prossiugsaid rolls together under heavy pressure, an endless flat belt passed between said rolls, and means acting in a plurality of angular directions for imparting dit irential elongation of opposite edges of said belt atthe nip olF'said rolls;

20. In a machine or the class describeih a pair of pressure rolls, an endless flat belt passed through the nip between said rolls, a

head rollover which said bolt passes and imparting an initial heavy tension thereto and steeringmeans acting steer the belt onto said head roll said steering means alsoactiug to impart a ditferential stretch to opposite edges of said belt.

21. In a machine of t 1e class described, a

said rolls tot belt passed gether under heavy pressure, a 1.1 between said rolls and means ac :terentially elongate oppo. 'te ed, belt as it passes through the nip between sa d. rolls to counteract lateral v 22. In a machine of the class described.v a pair of rolls, means for pressing said rolls together under heavy pressure, an endlrss llat belt passed between said. trolls, and means actuated, on lateral movement of said belt to diilercntially elongate opposite edges thereof to counteract said lateral movement.

23. In a machine of the class describech a pair of cooperating calender rolls between which a belt may pass a head roll, an endless belt passed about d head roll and through the nip between said calender rolls, means for initially tensioning said belt, and means "for imparting an additional variable tension diliiferentially between opposite edges there-oi to counteract tendency of the initially stretchedbelt to travel laterally in the nip to swing said roll to impart a d'i'li'erential stretching action to opposite edges of the belt to cause said belt to tend to assume a definite lateral. position relative to said calender rolls.

'25. In a machine of the class described, a pair of cooperating calende" rolls between which a belt may pass, a head roll urged away from the nip between said calender. rolls, an endless belt, passed between said calender of said on oil "l belt-Q a id calender rolls in either direction and over sari ender rolls.

.26. In a machine of the class described, a pair of COOlQQlTZtilllg calender rolls between which a belt may pass, a head roll urged away from the nip between said calender rolls, an endless belt passed between said. calender rolls and over said head roll and initially tensioned b said head-roll, a roll mounted to swing in. a plane and engaging said belt to form a gable therein unsymmetrically related to the plane of the swing of said roll, means controlled by the lateral position of said belt to swing said roll tov impart a differential stretching action to opposite edges of the belt cause said belt to tend to assume a definite lateral position relative to said calender rolls, nd means for predetermining said definite teral position. i

In machine 01: the class described a pair of cooperating caleiuler rolls between which a belt may pass, a head roll urged away from the nip between said calender rolls, an endless belt passed between said calender rolls and over said head roll and initially tensioned by said head roll, a roll mounted to swing in a plane and engagiu said belt to jorui a gable therein unsymmetrically re said belt and actuated by the longitiuliual travel of said belt to swing sai d roll to impart a dillerential stretching action to opposite ed ol': the belt to cause. said belt to tend to assume a definite lateral position relative to said calender rolls. c

28. In a machine of the class described, a pair oi"? cooperating calender rolls between which a belt may pass, a head roll urged away from the nip between. said calender rolls an endless belt passed between said calender rolls l head roll and initially tensioned by said head roll, a roll mounted to swing in a plane and O'l1 11l said belt to :torma gable therein unsymmetrically related to the plane of swing or said'roll, means controlled by the lateral position of said belt and actuated by the longitudinal travelot said belt to swing said roll to impart a dillerential stretching action to opposite edges oi? the belt cause said, belt to tend to assume a definite lateral position relative to said calender rolls and means for predetcrminiug said definite lateral position. I

- 29. In a machine of the class described, a pair of cooperating pressure rolls, a belt passed between the nip of said rolls, means to tenslon sa1d belt, a steering roll over which said belt passes and which forms a gable therein, said steering roll being movable in a plane unsymmetrically related to said gable, pairs of opposed friction wheels beyond opposite edges of said belt and normally out of contact therewith to be engaged and rotated by longitudinal movement thereof on lateral movement of said belt between the wheelsof either pair, and connections between said friction wheels and steering roll acting by the rotation of said wheels to move said steering roll in said plane to tend to steer said belt in a direction out of engagement with the actuated friction wheels.

30. In a machine of the class described, a pair of cooperating pressure rolls, a belt passed between the nip of said rolls,-means to tension said belt, a steering roll over which said belt passes and which forms a gable therein, said steering roll being movable in a plane unsymmetrically relatedto said gable, friction wheels beyond opposite edges of said belt and normally out of contact therewith to be engaged and rotated on lateral movement of said belt by longitudinal movement thereof, connections, between said friction wheels and steering roll acting to move said steering roll in said plane to tend to steer said belt in a direction out of engagement wlth the actuated friction wheels, anda follow up mechanism actmg to move said friction wheels out. of contact with said belt on the moving of said steering roll. 7

31. In a machine, of the class described, a pair of cooperating pressure rolls, a belt passed between the nip of said rolls, means to tension said belt, a steering roll over which said belt passes and which forms a gable therein, said steering roll being movable in a plane unsymmetrically related to said gable, pairs of friction wheels beyond opposite edges of said belt and normally out of contact therewith to be engaged and rotated on lateral movement of said belt by longitudinal movement thereof, connections between said friction wheels and steering roll acting by the rotation of said wheels to movesaid steering roll in said plane to tend to steer said belt in a direction out of engagement with the actuated friction wheels, and means for adjusting the normal positions of said friction wheels to determine the normal lateral position of sdid belt.

32. In a machine of the class described,

. gable,friction wheels beyond opposite, edges roof-said belt and normally out of contact therewith to be engaged. and rotated on leteral movement of said belt by longitudinal movement thereof, connections between said friction wheels and steering roll acting by the rotation of said wheels to move said steer passed between the nip of said rolls, means to tension said belt, a steering roll over which sa1d belt passes and which forms a gable therein, sa1d steerlng roll being-movable in a plane unsymmetrically related to said gable, friction wheels, beyond opposite edges of said belt and normally out of contact therewith to be engaged and rotated on lateral movement of saidbelt by longitudinal movement thereof, connections between said friction wheelsand steering roll acting bythe rotation of said wheels to move said steering rollin said plane to tend to steer said belt in a direction out of engagement with the actuated friction wheels, means for usting the normal positions of said friction wheels to determine the normal lateral position of saidbelt, and means for adjusting the spacing of said friction wheels to conform to various widths of belts. l

34. In a machine of the class described, a pair of cooperating pressure rolls, a head roll, an endless belt passed through the nip of said pressure rolls and over said head roll, means to impart a heavy initial tension to said belt, and means acting on the belt as it approaches saidhead rolland in response to lateral movement of said beltto steer it in the opposite direction to said lateral movement onto said head roll whereby a diagonal stretch in said belt is produced extending to the edge of the belt at said nip on the side to ward which said lateral movement is taking place, v y

,35. In a machine of the'clas s described, a pair of cooperating pressure rolls, ahead roll, an endless belt passedthrough the nip of said pressure rolls and over said head roll,

means to impart a heavy initial tension to said belt, andmeans acting on the belt as it approaches said head roll and inlresponse to lateral movement of said belt to steeritinthe opposite direction to said lateralmovemcnt onto said head roll whereby a diagonal stretch in said belt is produced extending to the edge of the beltat said nip on the side toward which said lateral movement is taking place, said steering means acting to ditieren tia-lly stretch opposite edges of said belt to 36. In a machine of the classdes'cribed, ,a'

pair-of cooperating pressure rolls, a head roll, a belt passed between the nip of said pressure rollsand over said head roll, means to tension said belt, a steering roll over which said belt passes and which forms a gable therein, means for permitting swinging movement of said steering roll in a plane unsymmetrically related to said gable, a pair of sets ot'l riction wheels disposed beyond the normal positions of the lateral edges of said belt, one or the other of said sets being engaged by the belt passing t-herebet-ween and rotated by longitudinal movement of said belt on lateral displacement thereon, and means actuated by rotation of said wheels to swing said steering roll in a direction to overcome said lateral displacement.

' 337. In'a'machine of the class described, a

pair of cooperating pressure rolls, a head roll, a belt passed between the nip of said pressure rolls and over said head roll, means to tension said belt, a steering roll over which said belt passes and which forms a gable therein, means for permitting swinging movement of said steering roll in a plane unsymmetrically related to said gable, a pair of sets ofi riction wheelsdisposcd beyond the normalpositions of the lateral edges of said belt, one or the'other of said sets being engaged and rotated by longitudinal movement of said belt onlateral displacement thereof, and means actuated by rotation of said wheels to swing said steering roll in a direction to overcome said lateral displacement and to move said engaged wheels in the direction of such displacement.

38. In a machine of the class described, a pair of cooperating pressure rolls, a head roll, a belt passed between the nip of said pressure rolls and over said head roll, means to tension said belt, a steering roll over which said belt passes and which forms a gable therein, means for permitting swinging movement of said steering roll in a plane unsym'metrically related to said gable, a pair of sets of friction wheels disposed beyond the normal positions of the lateral edges of said belt, one or the other of said sets being engaged and rotated by longitudinal movement of said belt on lateral displacement thereon,

' means actuated by rotation of said wheels to swing said steering roll in a direction to overcome said lateral displacement and to move said engaged wheels in the direction of such displacement, and means to adjust both sets laterally to define the normal position of said belt. v V 39. In a machine of the class described, a

pair of cooperating'pressure rolls, a head roll, a belt passed between the nip of said pressure rolls and over said head roll, means to tension said belt, a steering roll over which said belt passes and which forms a gable therein, means for permitting swinging 1novement-'ofsaid steering roll in a plane unsymmetrically related to said gable, a pair o'f setsof friction wheels disposed beyond the normal positions of the lateral edges of said belt, one or the other ofsaid sets being en gaged and rotated by longitudinal movement of said belt on lateral displacement thereon,

overcome said lateral displacement, and

means for adjusting the spacing of said sets of wheels to conform to belts of different widths.

- 40. In a machine of the class described, a pair of cooperating pressure rolls, a head roll, a belt passed between the nip of said pressure rolls and over said head roll, means to tension said belt, a steering roll over which said belt passes and which forms 'a' gable therein, means for permitting swinging movement of said steering roll in a plane unsymmetrically relatedto said gable, a pair oi sets of friction wheels disposed beyond the normal positions of the lateral edges of said belt, one or the other of said sets being engaged and rotated by longitudinal movement or said'belt on lateral displacement thereon, means actuated by rotation of said wheels to swing said steering roll in a direction to overcome said lateral displacement, and means for adjusting said sets of rolls together laterally of said belt.

41. In a machine of the class described, a pair of cooperating pressure rolls, a head roll, a belt passed between the nip of said pressure rolls and over said head r0ll,'means to tension said belt, a steering roll over which said iio ing the spacing of said sets of wheels tocon- I "form to belts of ditlerentwidths, and means for adjusting said sets of rolls together laterally of said belt. I

42. In a machine of the class described, a pair of cooperating pressure rolls, a head roll, a belt passed between the 'nip of said pressure rolls and over said head roll, means'to tension said belt, a steering roll over which said belt passes and which forms a gable therein, means for permitting swinging movement of said steeringro'll in a plane unsymmetrically related to said gable, a pair of sets of friction wheels disposed beyond the normal positions of the lateral edges of saidbelt, one orthe otherof said sets being engaged and rotated by longitudinal movementfof said belt on lateral displacement thereon,:rneans actuated by rotation of said wheels to swing said lateral displacementand to move said engaged wheels in the direction of such displacement, and means to adjust the'spacing of said sets to conform to belts of diiferent widths.

In a machine of the class described, a pair of cooperating pressure rolls, a head roll, a belt passed between the nip of said pressure rolls and over said head roll, means to tension said belt, a steering roll over which said belt passes and which forms a gable therein, means for permitting swinging movement 01 said steering roll in a plane unsymmetrically related to said gable, a pair of sets of friction wheels disposed beyond the normal positions of the lateral edges of said belt, one or the other of said sets being engaged and rotated by longitudinal movement of said belt on lateral displacement thereon, means actuated by rotation of said wheels to swing said steering roll in a direction to overcome said lateral displacement and to move said engaged wheels in the direction of such displacement, means to adjust both sets laterally to define the normal position of said belt, and means to adjust the spacing of said sets to conform to belts of diiferent widths.

4A. In a machine of the class described, a pair of cooperating pressure rolls, a head roll, a belt passed between the nip of said pressure rolls and over said head roll, means i to tension said belt, a steering roll over which said belt passes and which forms a gable therein, means for permitting swinging movement of said steering roll in a plane unsyn'imetri'cally related to said gable, a pair of sets of friction wheels disposed beyond the normal positions of the lateral edges of said belt, one or the other of said sets. being engaged and rotatedby longitudinalmovement of said belt on lateral displacement thereon, means actuated by rotation of said wheels to swing said steering roll in a direction to overcome said lateral displacement and to move said engaged Wheels in the direction of such displacement, and means to adjust both sets laterally to define the normal position of said belt.

In testimony whereof I have'afiixed my signature.

JOHN GURNEY 1 CALLAN.

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