US3025791A - Variable web tension for uniform layoff - Google Patents

Description

March 20, 1962 e. N. AUERBACHER 3,025,791

VARIABLE WEB TENSION FOR UNIFORM LAYOFF Filed Sept. 9, 1957 44 F/zh/ 42 50 f8 66 54 6 52 60 20 24 2 40 k k g l I) I 1 I l l l 1 1 l I I L Q L i ATTOR/VAE'XS.

United rates Patent Q" 3,025,791 VARIABLE WEB TENSION FOR UNIFORM LAYUFF George N. Auerhacher, pringfield, N.J., assignor to Champlain Company, inc, Bloomfield, N.J., a corporation of New York Filed Sept. 9, 1957, Ser. No. 682,958 6 Ciaims. (Cl. 101-131) This invention relates to web feeding apparatus, and more particularly to apparatus for applying variable tension to a Web in order to help secure registration of multiple operations on said Web.

The primary object of the present invention is to generally improve apparatus for feeding a web receiving multiple operations which are required to be in registration. A typical example is multicolor printing, requiring a so-called print-to-print register. Other examples are scoring, creasing, punching and cutting of a web which has already been printed, thus requiring a so-called cutto-print register. Often the web is both printed in multiple colors, and scored and punched, etc.

The usual practice has been to maintain constant web tension. It has been recognized that a web may yield if subjected to increased tension, and accordingly, elaborate apparatus has been devised, including dancer rolls, tensionometers, and other means, to maintain constant Web tension.

To maintain registration, running registers have been provided between a common drive shaft, and the individual units of a press line driven by said shaft. Thus, additional motion or velocity may be added or subtracted at any unit to keep it in proper registration. To do this at high web speeds, photoelectric scanners have been devised which are located between units, and which automatically feed positive or negative motion at the running registers as may be required to maintain registration.

The primary object of the present invention is to generally improve apparatus for the feed of a Web undergoing multiple registered operations. A more specific object is to greatly reduce the work required of the registration control means, that is, the photoelectric scanners and running registers, etc. I find that the yield of the web is not constant when subjected to a uniform tension, and instead varies markedly with other factors, notably the moisture content. In accordance with my invention, the web is not subjected to uniform tension, and instead the tension is varied in that direction which tends to achieve a constant web yield.

I have found that it will not do to secure a measurement of Web yield at the end of the press line, and to then vary the web tension, for the characteristics of the web do not remain uniform. Such a correction may be made far too late, because by the time the correction is made, the material entering the press line may differ in characteristics. This is particularly true in the case of a gravure press line, with its complicated web lead through driers at each of the presses, causing the total length of Web in a press line to be very great.

In accordance with my invention, tension is applied to the web ahead of the press line, and the yield of the web is measured at a point near the first unit in the press line. Thus, the tension is appropriately varied at the beginning of the press line, and the great length of web in the press line itself is of no consequence.

To accomplish the foregoing general objects, and more specific objects which will hereinafter appear, my invention resides in the apparatus for applying variable web tension, and the elements thereof, as are hereinafter more 3,@Z5,791 Patented Mar. 20, 1962 particularly described in the following specification. The specification is accompanied by a drawing in which:

FIG. 1 is a plan view of a multicolor press line embodying features of my invention;

FIG. 2 is a side elevation of the same;

FIG. 3 is a schematic fragmentary side elevation drawn to larger scale;

FIG. 4 is a fragmentary view showing a modification;

FIG. 5 is a schematic diagram explanatory of another modification; and

FIG. 6 is a schematic diagram explanatory of still another modification.

Referring to the drawing, and more particularly to FIGS. 1 and 2, a web 12 is unwound from a large reel 14, and then passed through appropriate units such as a splicer 16, decurler 18 and a pull unit 20. The roll 14 may be mounted on a roll carrier 22 designed to facilitate changing from one roll as it expires, to a new roll as shown at 2:3. The expired roll may then be removed and replaced by another full roll preparatory to expiration of the second roll, and so on.

The web feed or pull unit 29 is arranged for fine speed adjustment, as by means of an infinitely variable drive 24. There is usually a slack loop 26 ahead of the feed unit 20. The web then goes to a series of units for multiple operations on the web. In the present case, a multicolor gravure press is shown, comprising printing units 30, 32, 34, 36 and 3'8. These are followed by a pull unit 40, which may be followed by still further units not shown, for scoring, creasing, punching or/and cutting the web.

Referring to FIG. 1, the units of the press line and both pull units are all driven in unison by a common drive shaft 42, driven by a motor 44, through suitable belts 46. The gearing between the shaft 42 and the gravure cylinder shafts is shown at 50, 52, 54, 56, 58, respectively. This ordinarily includes running register mechanism of the differential gear type, so that additional motion may be fed in by means of remotely controlled reversible correction motors, indicated at 60, 62, 64, 66 and 68. Running register 50 and motor 60 on the first unit 30 are not essential, but may be used for convenience and uniformity. The differential gear running registers need not be described in detail, for they are well known in the art, and reference also may be made to US. Patent No. 2,163,035 issued to William F. Grupe on June 20, 1939, and entitled Apparatus for Effecting Register of Multiple Operations.

To automatically control the correction motors, the web may be scanned by suitable scanners housing photoelectric cells or eyes indicated in FIG. 2 at 72, 74, and 76. These form part of a registration control apparatus which may be of the type disclosed in US. Patent 2,348,862 granted to Morris Sorkin on May 16, 1944, and entitled Registration Control Apparatus. In that apparatus, the position of a mark on the web is compared or related to the position of a mark on the print cylinder shaft, and for this purpose, each print cylinder shaft is provided with a so-called phase detector unit. These are indicated in FIG. 1 at 82, 84, 86 and 88. Such units (scanner and phase detector) are not needed for the first press unit 30, because the problem is to keep the subsequent units in registration with the first unit.

In lieu of comparing the position of a mark put down on the web by the first unit, with the position of a mark on the second cylinder, it may be compared with a second mark put down on the web by the second cylinder (which, of course, is an indication of the position of the scond printing cylinder). Such a system is disclosed in US. Patent 2,151,570 granted March 21, 1939, to D. R. Shoults et al. and entitled Control System. For

purposes of the present invention, there is no significant difference between a system using scanners to compare two marks on the web, and a system comparing a single mark on-the web with a phase detector. Either system will similarly control a correction motor to add positive or negative motion to the drive of a unit, and thus speeds it or slows it slightly in order to hold it in register.

Structurally, there would be a difference in the addition of another scanner following the last printing unit 38, this being indicated at 78 in FIG. 2. This added scanner 78 would replace the phase detector shown at 88 in FIG. 1. In passing, it may be mentioned that even with phase detectors, the web scanners may be used (though less desirably) following their respective phase detector, instead of preceeding the same, in which case the scanners 72 through 78 would be used with the phase detectors 82-88. The disadvantage is that the comparison for registration and the resulting correction are made later, after an additional length of web corresponding to that used in one printing unit.

It has long been the usual practice and understanding of the industry that the web should be maintained under constant tension in order not to introduce another variable into the problem of registration. Elaborate precautions have been taken to maintain constant tension. Thus, refering to FIG. 2, feed unit 28 is followed by a dancer roll 90. This is given a weight corresponding to double the desired web tension, or may be made of excessive weight and then counterbalanced by springs or a weight arm such as that indicated at 92. The dancer roll 99 is mounted for vertical movement, and may be provided with limit switches. The PIV (positive infinitely variable) drive 24 has a remotely controlled reversible adjusting motor 25, and the limit switches at dancer roll 90 are connected to motor 25. Thus, the feed velocity is increased when the dancer roll 90 rises, and is decreased when it falls, in order to keep the dancer roll suspended at a mid point where its weight determines the tension of the web. The element 25 may be hydraulic, in which case its valves are electrically controlled, with the same result.

Contrary to this prior practice, I have found that the maintenance of registration by the scanners and running registers is greatly aided by varying the tension applied to the web in such direction as to maintain constant yield of the web. Thus, referring to FIG. 3 of the drawing, the dancer roll 90 is mounted on an arm 92 pivoted at 94, and carrying weight 96, but the latter is movable along arm 92 by means of a screw 98 turned by a small adjusting motor 100. The latter is preferably mounted on and movable with the arm 92, and it is remotely controlled in a manner explained later, the control being in response to a measurement of the yield of the web.

Reverting to FIG. 1, it will be seen that the first unit is provided with a phase detector 80. The first unit 30 prints a marker on the web. As is already understood in this art, this may be a special marker, or it may be an edge of the printed matter which is anyway being printed by the first unit. In either case, this marker repeats itself along the web, and after a suitable number of repeats, corresponding to the length of the web in the first unit 30 including its drier, the web reaches the scanner 70. If the yield of the web has increased, the marker moves ahead, or differently expressed, the number of layoffs of the printed matter to the scanner becomes less (and vice versa when the web yield has reduced for the same tension).

The location of the scanner relative to the marker might perhaps be used as a measurement, but this is not satisfactory in practical operation, because it presupposes a fixed orientation or timing of the printing cylinder 102, which instead may be random when the press line is first being threaded with a web. Instead, the first printing cylinder is provided with a phase detector 8t), and thus the location of the marker may be compared with a marker on the press cylinder. This is indicated in FIG. 3 by the marker Hi4 observed by a scanner 1%. These elements 104, 106 represent the phase detector 8%, in highly simplified schematic form. An actual phase detector is better described in the aforesaid Sorkin Patent 2,348,862.

The output of the circuitry there described provides correction current to operate a correction motor in one direction or the other, and similarly in the present case, referring to FIG. 3, the scanner 7% is connected to suitable control circuitry housed at 188, and the phase detector 106 is connected to said circuitry, as is indicated by the broken line 110. The output from circuitry 188 is supplied through cable 112 to the correction motor 1M). Thus, the weight 96 is shifted back and forth to vary the tension on web 12 in that direction which tends to maintain the yield of the web constant.

Both the measurement and correction of tension are preferably performed at the beginning of the press line. This is so because a great length of web is used in the press line itself, particularly with gravure printing units. A measurement of yield at the discharge end of the press line may lead to a correction so late that the material entering the press line is already of different characteristic (say moisture content) and yieldability.

Two separate scanners may be used between the first and second presses, one scanner for use with the phase detector (FIG. 1) for web yield control, and one for use with the phase detector 82 for registration correction. However, inasmuch as a single scanner may be wired to both circuits or control panels, I here show one scanner at 78, (FIGS. 2 and 3) serving both purposes.

Referring to FIG. 3, the first Web scanner 70 is connected not only to the circuitry housed at 168 for control of motor 180 which maintains the web yield, but also to conventional circuitry housed at 18419 which controls a remote reversible correction motor 62. This is the motor also shown in FIG. 1 associated with the running register differential gearing at 52 for feeding positive or negative motion to the printing cylinder of press 32. For this purpose, the web scanner 7% makes its comparison with a phase detector 82 (FIG. 1) on the second press 32. The parts of this phase detector 82 are represented schematically in FIG. 3 by the target 182 which turns with the printing cylinder 1%, and an electric eye 186 which cooperates with target 182. The phase detector may be of more elaborate construction such as that shown in Sorkin Patent 2,348,862 previously referred to.

FIG. 4 discloses a modification in which the measurement of web yield is performed even earlier than in the arrangement shown in FIGS. 13. The pull unit 20' is modified by the addition of a special means to apply a marker to the web. This may be a simple print wheel 120, inked by rollers 122. The dancer roll is mounted on a Weighted arm 92, carrying a correction motor all as previously described. However, the scanner 70' is located ahead of the first printing unit 30', instead of following it. It is responsive to the layoff of the marker produced by wheel 120. For purpose of comparison, the shaft of the latter is provided with a phase detector, schematically indicated at 184', 196'. It will be understood that the scanners 70' and 166' are connected to appropriate control circuitry, the output of which leads to the correction control motor 101), all as previously described, and that the direction of operation of the motor so selected that the tension applied to the web is varied in that direction which tends to maintain the yield of the Web constant. In such case the next scanner 70 is used with phase detector 82, solely for registration correction, and there is no phase detector 80.

The system shown in FIG. 4 has the advantage of obtaining a measurement ahead of the first printing unit, but it has the disadvantage of requiring special apparatus to apply a marker to the web. In most practical cases, therefore, I prefer the system shown in FIG. 3, in which the printing which is laid down by the first printing unit acts also as a marker. In either case, the yield of the web is measured at a point close to the first printing unit.

It will be understood that there are other ways to vary the tension applied to the web. The gravitational dancer roll shown in FIGS. l-4 is only one of several ways of varying tension. FIG. 5 shows tension applied by means of a hydraulic or air cylinder 130. The feed unit 20 corresponds to that previously shown, and is similarly driven by variable speed means such as a PIV drive. The roll 132 corresponds to the dancer roll 90, but is urged downward by a piston 134 in cylinder 130. The fiow of hydraulic fluid or compressed air to cylinder 139 is controlled by suitable electrically operated valve mechanism, and the valves are remotely controlled much as previously described. The means to measure the elongation or yield of the web may take the form shown in FIG. 3, or the form shown in FIG. 4, and the output of the control circuitry 108 (FIG. 3) is applied to the valve mechanism controlling piston 134. When the yield is reduced, the pressure applied to piston 134 is increased, and vice versa.

Still another method of controlling the tension exerted on the web is illustrated in FIG. 6 of the drawing. This makes use of a so-called tensionometer. The tensionometer comprises three rollers 1441, 1'42 and 144. The latter two are stationary, while roller 140 is kept under spring tension, as by means of a compression spring 146. It will be understood that when web tension is reduced, roller 140 may move to the right, and when web tension is increased, the roller 140 is moved to the left. The motion of the roller may be detected by suitable means, here shown as a floating contact 148 moving between stationary contacts 150 and 152. The tensionometer could be adjusted by changing the pressure of spring 146, as by rotating the stop 154 on a threaded shank 156. Alternatively, the stop 154 may be left alone, and the position of the stationary stop 158 could be varied.

Such tensionometers have heretofore been used to maintain constant tension on the web. For example, circuitry indicated at 160 may lead from the contacts 150, 152 to a correction motor 162 driving a worm 164 meshing with a worm gear 166, which turns a screw 168, carrying a roller 170. This corresponds in function to the dancer roll 90 previously shown in FIGS. 1-4, and follows the feed unit 20.

In the present case, however, the position of the contacts 150, 152 is itself made adjustable by means of a small correction motor 172 driving a screw 17 4. The correction motor 172 is controlled by the output of control circuitry indicated at 108 (as in FIG. 3), and is operated in such direction as to vary the tension in proper direction to maintain constant web yield.

It will be understood that the apparatus shown in FIG. 6 further includes a scanner corresponding to 70 in FIGS. 3 and 4, and a phase detector corresponding to 104, 106 in FIGS. 3 and 4, operating to measure the actual yield of the web. This in turn is used to vary the web tension to which the tensionometer is adjusted, this being done by correction motor 172. The tensionometer seeks through motor 162 to maintain uniform web tension, but the tension which it is seeking to maintain, is itself quantitatively varied by correction motor 172.

In general, the web tension at the dancer roll 90 (or 90', 132 or 170) is preferably as great as at any following point in the press line. The pull unit 40 (FIGS. 1 and 2) will slip if turned at a linear speed greater than the web speed, and in the present case the grip of the pull unit 40 on the web is kept low enough so that the said slippage takes place at a web tension no higher than that at the dancer roll 90. Similar remark applies to the Web tension in the presses, and if need be, the dancer roll is weighted to produce an initial web tension sufiiciently high. This practice is not essential, but has the advantage of inhibiting additional yield or elongation of the web after the yield has been brought to a uniform amount by the apparatus here disclosed.

It is believed that the construction and operation of my improved apparatus, as well as the advantages thereof, will be apparent from the foregoing detailed description. The usualrunning register mechanism is retained, and is preferably automatically controlled by the usual electric eye scanners. These may be of the double marker type (Shoults Patent 2,151,570), or of the single marker and phase detector type (Sorkin 2,348,862). In general, the phase correction thus afforded represents a temporary change in speed at any one unit, to effect a change in position at that unit, in order to achieve registration. The amount of correction thus required is greatly reduced by maintaining the web under variable tension instead of constant tension, with the tension varied in proper direction to maintain constant yield of the web. I have found that it is most helpful to measure the yield, and also to correct the tension for constant yield, at or near the input of the press line, particularly when, as is usually the case, there is a great length of web in the press line itself. For this purpose, a marker is put on the web ahead of or in the first machine, and is scanned at a point only a little beyond the application of tension to the web, in order to measure the actual yield or elongation of the Web by the position the marker asumes after a number of repeats of the marker. The change in elongation thus measured is employed to change the tension applied to the web. In most practical cases, the first unit operating on the web in a printing unit, and the print produced by that unit may itself be used as the desired marker. The same marker may later be used for registration correction.

The means for correcting registration at each press need not necessarily be a running register of the differential gear type. Another common expedient for this purpose is a movable compensator roller which slightly lengthens or shortens the web between one press and the next. For this purpose, the bearings of the compensator roller may be moved by screws, turned by a remotely controlled reversible correction motor, working through high ratio reduction gearing.

It will be understood that while I have shown and described my improved apparatus in several preferred forms, changes may be made in the structures shown without departing from the scope of the invention as sought to be defined in the following claims. In the claims, the term marker is intended to include a selected part of desired printed matter, as well as a marker used solely as a marker.

I claim:

1. In the operation of multiple machines working in repeat lengths on a continuous moving web, the method of helping maintain uniform layoff of the repeat lengths which includes applying a maintained tension to the web before the first machine, putting a marker representing the repeat length layoff on the web in the first machine, scanning the marker between the first and second machines in order to measure the yield or elongation of the web by the position of the marker, and varying the aforesaid maintained tension applied to the web before the first machine in proper direction to maintain constant layoff.

2. In the operation of a multicolor gravure printing press working in repeat lengths on a continuous moving web and including driers housing long lengths of said web, the method of helping maintain uniform layolf which includes applying a maintained tension to the Web before the first unit of said press, putting a marker on the web in the first unit, scanning the marker between the first and second units in order to measure the yield or elongation of the web by the position of the marker, and varying the aforesaid maintained tension applied to the web before the first machine in proper direction to maintain constant layolf.

I? 3. For use with multiple machines working in repeat lengths on a continuous moving web, a web reel support, a pull unit, an adjustable dancer roll to apply a maintained tension to the web ahead of the first machine, re-

. yield or elongation of the web by the position of the marker, and means responsive to said scanning device for so operating said remotely controllable means as to vary the aforesaid tension applied to the web ahead of the machines by the aforesaid tension applying means in proper direction to maintain constant layoff.

4. For use with a multicolor gravure printing press working in repeat lengths on a continuous moving web and including driers housing long lengths of said web, means for applying a maintained tension to the web ahead of said press line, remotely controllable means to vary said maintained tension, means to put a marker rep resenting a repeat length layoff on the web at the first machine, a scanning device to scan the marker between the first and second machines, and to thereby measure the yield or elongation of the web by the position of the marker, and means responsive to said scanner to so operate said remotely controllable means as to vary the aforesaid maintained tension applied to the web ahead of the press line in proper direction to maintain constant layoff.

5. For use with a multicolor gravure printing press Working in repeat lengths on a continuous moving web and also including register means at the printing units with photoelectric scanners and associated circuitry in order to maintain register, a web reel support, a pull unit,

an adjustable dancer roll for applying a maintained tension to the web ahead of said press line, remotely controllable means to vary the adjustment of said dancer roll in order to vary said maintained tension, means to put a marker representing a repeat length layofl on the web at the first machine, a scanning device to scan the marker between the first and second machines, and to thereby measure the yield or elongation of the web by the position of the marker, and means responsive to said scanner to so operate said remotely controllable means as to vary the aforesaid maintained tension applied to the web ahead of the press line in proper direction to maintain constant layoff.

6. For use With a multicolor gravure printing press working in repeat lengths on a continuous moving web and including driers housing long lengths of said web and also including register means at the printing units with photoelectric scanners and associated circuitry in order to maintainregister, means for applying a maintained tension to the web ahead of said press line, remotely controllable means to vary said maintained tension, means to put a marker representing a repeat length layofi' on the web at the first machine, a scanning device to scan the marker between the first and second machines, and to thereby measure the yield or elongation of the web by the position of the marker, and means responsive to said scanner to so operate said remotely controllable means as to vary the aforesaid maintained tension applied to the web ahead of the press line in proper direction to maintain constant layoit, said first web scanning device being operatively connected to one of the register maintaining means to act also as the first of the web scanners used for maintaining register.

References Cited in the file of this patent UNITED STATES PATENTS 2,041,602 Grozier May 19, 1936 2,105,185 Degnan Jan. 11, 1938 2,203,706 Stockbar-ger June 11, 1940 2,375,451 Waters May 8, 1945 2,429,500 Wolfner Oct. 21, 1947 2,522,479 Crafts Sept. 12, 1950 2,549,605 Huck Apr. 17, 1951

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