US2312310A - Papermaking - Google Patents

Description

25o-201 Au 252 EX SSREFERENCE v r l 5 q 'Muh 2,1915. 'Y

lD. B. BRADNER TAL 2,312,310

PAPER MAKING und um 1f 195s s sneetpsnm 1 cRoss REFERENCE Examiner D. B. BRADNER Erm. 2,312,310

PAPER MAKING Filed march 1, 19:59 's'sneets-sneet 2 ./Q" J M/orff ATTORNEYS gw, .w f @Ross REFERENCE P Examiner Patented Mar. 2, 1943 Donald B. Bravdner and George C.- Munro, Hamilton, Ohio, assigner-s to The Champion Paper and Fibre Companyf-Hamilton, Ohio, a. corpora. e

tion of Ohio Application March 1, 1939, Serial No. 259,154

6 Claims.

This invention relates to paper making and has particular reference to apparatus for controlling the gloss-producing operations performed on the paper in accordance with the gloss characteristlcs of finished paper issuing from the calenders in a manner to glve a gloss of hitherto ungttainable. uniformity to the finished paper we Y One of the most important properties of paper is its gloss, and more particularly the uniformity of the degree of gloss it possesses. The gloss characteristic isindicative to a great degree, .not only of the appearance and feel of the paper, but also of the surface smoothness, density, and other of the properties which determine the printing quality thereof. Thus, if the manufacture of-paper is controlled to give a uniform degree of gloss, greatly enhanced uniformity of these other properties is also secured and the iinished paper is of exceptional value to the printer because of the more uniform and dependable printing results which are possible thereon. t

Gloss is produced by passing coated or uncoated paper between pressure rolls in a calender. The degree of gloss imparted to the paper by the calender may be varied within limits by increasing or decreasing the pressure exerted by the rolls on the, paper. However, the gloss characteristic does, not remain constant with constant calender pressure. Variations in moisture content, in composition, density, and other properties of the stock and the coating, all change the gloss characteristic produced by a given calender pressure. Because all of these properties are seldom, uniform throughout any considerable area in paper as commonly made, corresponding variations in gloss are imparted to different portions of a paper web even though a constant value of calender pressure is maintained.

It has been the practice in paper making to regulate the gloss imparted to paper by periodically taking samples from the paper web issuing from the calender, visually comparing the gloss thereon with that on standard samples, and adjusting the calender pressure in an elort to correct gloss variations. Such samples are frequently not typical of all the paper in the roll. The accuracy of such visual comparisons depends largely on thev skill of the operator and is necessarily subject to wide variation. Further, the

taking and examination of samples usually in- ,l volves stopping the paper web, which slows down in taking the sample and making comparison permits a considerable length of paper web to pass through the calender before a corrective adjustment can be made. The diiculties and disadvantages inherent in the method of controlling the gloss by sampling and making 'visual comparisons are more serious the higher the paper speeds, and have become moreimportant with the modern demand for greater speeds and higher quality. For the reasons described it is almost impossible to produce by methods heretofore known, paper having a satisfactorily uniform degree of gloss. t

It is the primary object of the present invention to provide apparatus for continuously producing finished paper having a substantially uniform gloss. More specifically, the invention contemplates apparatus for producing a continuous web of paper having a gloss characteristic which does not vary beyond predetermined and controllable limits, and for effecting such production without the interruptions to operation required in taking samples for visual comparison. To this end, the apparatus of the invention provides a substantially continuous control of the 4calender' pressure and in some cases the surface dryness of the paper being calendered Which'corrects deviations of gloss from the desired degree as soon and as often as such deviations occur, and not only avoids the wide variations -in gloss inherent in prior practices but prevents `changes in gloss which could not even be detected by the customary visual inspection.

A further object of the invention is the provision of means substantially continuously readjustment of the difference in pressure exerted' by the rolls on opposite side portions of the paper web, which pressure difference is maintained while the values of absolute pressure on both sides of the web are simultaneously varied in accordance with changes in the gloss characterstic. 50`

In general, the objects of the invention are carried out by variably adjusting the pressure exerted on the paper, and in some cases the dampness of the surface of paper in the calender in response to and in accordance with all signicant changes in the gloss characteristic of the paper issuing therefrom. This is preferably accomplished by continuously specularly reilecting a beam of light from the finished surface of the moving paper web issuing from the calender and varying the pressure applied to the calender rolls by means responsive to changes in the intensity of the reflected light beam. In accordance with a modification of the invention, the corrective capacity of the apparatus is increased by altering the surface moisture of the paper web entering the calender in response to gloss variations when adjustment of calender pressure is insufcient to produce the required correction, and the change in surface moisture may comprise the primary corrective adjustment rather than the change in calender pressure, if desired.

The only gloss producing factors that are variably controlled in accordance with the present invention are the calender pressure and the surface moisture of the paper passing through the calender. Accordingly, the term gloss producing capacity is used in the appended claims to dene the capacity of either the calender pressure or the surface moisture of the paper entering the calender or both of these factors to affect the degree of gloss produced on the paper surface, and this term does not include the capacit-y of other factors to affect such degree of gloss.

In describing the invention in detail, reference will be made to the accompanying drawings, in which certain embodiments thereof have been illustrated. In the drawings:

Figure 1 is a diagrammatic and simplified representation of one form of apparatus for carrying out the invention, embodying a paper calender in which the roll pressure is hydraulically applied and adjusted;

Figure 2 is a sectional view of the calender illustrated taken on line 2-2 of Figure 1;

Figure 3 is a wiring diagram of the apparatus illustrated in Figure 1;

Figure 4 is a diagrammatic and simplified view of a part of a paper calender illustrating the controlled addition of moisture to the paper web; and

Figure 5 is a Wiring diagram, similar to Fig. 3, showing an arrangement adapted to opera-te surface moisture supply adjusting means only when pressure adjustment is inadequate to give the desired degree of correction.

Referring to Figures 1 and 2, the calender comprises the usual stack of rolls II which may be of metal or of metal alternating with cornpressed paper, cotton, or other suitable material, mounted in a framework I 2. The calender illustrated may be either a machine calender at the end of a paper making machine or a supercalender separate from a paper making machine. The rolls II all rest upon the lowest roll which is journaled in the frame I2 and is driven by a suitable source of power in a known manner. A paper web I3 enters the calender at the top, passes between the successive pairs of rolls and leaves at the bottom in the usual manner, passing over a truly running y roll or equivalent means I4. In order to increase the pressure exerted upon the paper beyond that imposed by the weight of the rolls themselves, blocks I5 are provided over the journals of the top roll I I` and pressure is applied to these blocks through rods I6 by pistons I1 which operate in hydraulic cylinders I8 and I9. Hydraulic pressure in the cylinders I8 and I9 is provided by iiuid supplied through pipes 2| and 22 leading separately to LMUDD IlI' LRLHUL the two cylinders I8 and I9 which apply pressure to the opposite ends of the rolls. The pressure on each end of the rolls is separately controlled by separate valves 23 and 24 which receive fluid from a high pressure supply 25 and supply it to the respective cylinders I9 and I8, at controlled pressure through pipes 2I and 22. This may be accomplished by various pressure regulating means such, for example, as that shown in a copending application of George C. Munro, entitled Hydraulic calender," Serial No. 259,156, filed concurrently herewith. Pressure regulating apparatus of the type there disclosed has been diagrammatically represented herein. The apparatus is so constructed that when the shafts 4I and 42 of the valves 23 and 24 are rotated in one direction or the other, the pressure applied from the supply 25 to the calender pressure cylinders I8 and I9 is increased or decreased, the change in pressure being proportional to the amount of rotation of the valve shafts. The shafts 4I and 42 of the valves 23 and 24 are rotated by the gears 21 and 28 respectively, and the gears are driven in unison to give equal simultaneous variation to the pressure on opposite ends of the calender rolls, by the gears 29 and 30 mounted on shaft 3| which is rotated in either direction desired by gear 32 mounted on the shaft of a reversible motor 33 which is operated as more fully hereinafter described.

If it is desired to vary the pressure on one end of the roll with respect to that on the other end, this is accomplished by manually pressing knob 34 and throwing gear 29 out of mesh with gear 21. Gears 28 and 30 and shaft 3| then remain stationary while gear 21 is being rotated to adjust valve 23. As soon as pressure on knob 34 is released gear 29 is returned into mesh with gear 21 by spring 35, Further operation of motor 33 then adjusts the pressure on both ends of the calender rolls simultaneously, maintaining the pressure differential as set.

'Ihe pressure on both ends of the rolls may be quickly thrown on or off as desired, without changing the adjustment by throwing valve lever 36 to the on or off position as indicated in Figure 1.

For the guidance of the operator, pressure gauges 31 and 38 may be provided, advantageously connected to the pipes 2| and 22 through pressure snubbers 39 and 40, which may be in the form of small orifices, and which protect the gauges against sudden pressure changes.

Means are provided for continuously detecting the gloss characteristic of the paper web issuing from the calender, and controlling the calender pressure in response to changes in the gloss characteristic. It has been found that this can be accomplished by directing a beam of light from a source of constant intensity on to the finished paper web surface, and variably controlling the calender pressure by means responsive to the amount of light from such beam which is specularly reflected from the paper web surface. 'I'he means provided for detecting the intensity of the reflected light preferably comprises a photoelectrio cell or cells, and the arrangement is preferably such that the controlling light is reflected from an area which extends for a considerable distance transversely of the moving paper web. Excellent results are obtained by the use of light directing and detecting apparatus and paper web supporting means of the type disclosed in our copending LAllllllX/l application Serial. No. 259,155 entitled Gloss meter. and filed concurrently herewith, now Patent No. 2,246,591, granted June 24. 1941. Ap.- paratus of this type has been illustrated in Figure 1 in a diagrammatic and simplifier manner..

inga high intensity source of light of small area..

The lamp 5i is supplied with current from a line s; t energized by a constant voltage regulator or other known means of maintaining constant voltage, not shown, through an autotransformer orl a variable resistance 52 which can be used to adiust the intensity of the light for reasons hereinafter pointed out. A voltmeter 53 may be wired in parallel with the lamp 5I to indicate the applied voltage for the convenience of the oper- M01'.

In order that the intensity of the light 5I may be maintained at a constant value in accordance with the adjustment, a photoelectric cell 55 is mounted adjacent the light. The output of this cell is measured on a microammeter 55. In order that the operator may readily detect variations from. the correct value of light intensity, a variable resistance 5l is placed in parallel with the -meter and used to bring it to a standard reading advantageously at the center of the scale after the light intensity has been adjusted to the correct value as hereinafter described. Any variations which may occur in the intensity of light source 5I, due to aging of the lampor other cause, will be immediately made apparent by a departure of the microammeter 56 from the standard reading. The operator can then restore the light intensity to its proper value by adjustment of the resistance 52.

The paper web is suitably supported at theY point of detection in such a manner that its reflective surface is held in a xed and definite position regardless of the speed of travel of the web. This may be accomplished by passing the web under tension over a fly roll I4. The light from the lamp 5I is concentrated and directed by suitable means into a beam which strikes the paper web along a path of considerable length extending transversely of the web. The lightv from this beam, which is reflected by the paper surface, passes through a tubular shield 5B and falls on a photoelectric cell 59 which is connected by wires` k and l tothe meter and photoelectric relay box designated as av whole by the numeral $9.. The relay box 60 is connected by wires b, i and i to. a control panel designated as a whole by the numeral IIII, which panel in turn is connected by wires i. and y' to a control box |00 which serves to control motor 33 and which isY advantageously energized from a three phase power. line a, g, h. The panel lvl-0 is also energized by leads a and h from the said three phase circuit, for. purposes hereinafter described.

Thev manner in which these devices function to cause operation of motor 33 to increase the calender pressure when the gloss is below a predetermined lower limit and to decrease the calender pressure when the gloss is above a predetermined upper limit will be understood by reference to Figure 3. In this figure broken lines 6U, IUI) and. IIB enclose those elements.v which on the paper leavingthe calender.

60;. |90 and Hl in Figure l, except that to simplify the? diagram switch I2I is shown in Figure 3 within the limits ofpanel IIIJ whereas it is actually located outside this box in connection with valve :handle-:idasV indicatedin Figure 1.

Reference will rstbe made to the circuit forl measuringthe current output of the photoelectric cell' 59, which? current is a measure of the gloss This photocell, as pointed out in our copending Gloss meter" applicatiommay be ofA any desired type, but iszadvantageously of thefblocking layer type in which t-he output depends upon the light falling on the cell, but which does not require the addition of potential from an outside source. For

example, a cell of' the type described in United.

States Patent No. 2,034,334, has been found suitablefor this purpose. The output of this cell may beI measured by any suitable device, but this is. advantageously accomplished by someftype oi' potentiometer circuit. A simple type of potentiometer is shownfor purposes of illustration, .but itwill be understood by those skilled in the artthat other special or modified types of circuit may be used if desired. In the circuit illustrated in Figure 3, a. resistance 6I is placedl across the terminals of the cell 59. A variable resistance 6.4 serves to regulate current from battery 65 in the. circuit including resistance 64. and slide wire 68. The instrument is standardized by connecting standard cell` 62 in the circuit by moving switch 63 to the right in Figure 3, setting slider 61 on slide Wire E8 at. a point which corresponds. to the potential of the standard cell, and then adjusting4 resistance 64 until the galvanometer IiSvreads zero. After the instrument is standardized switch 63 is. moved to the left in Figure 3, thus connecting photocell 59 in the circuit in place of standard cellA 62. Ii the slider 61 is left inthe same position the galvanometer 66 will read zero. when thepotential maintained by photocell 59 across the resistance 6I is equal to the, potential of standard cell 62. The values of resistance in the potentiometer circuit, the constants ofthe photoelectric cell 59, the scale of the slide wire rheostat 6B andv the intensity of the4 light source 5I are all so chosen and adjusted that the position of the slider 61 at which the galvanometer 66 is not deilected in either directi'on, directly indicates the degree of gloss on the paper as dened by the intensity of light reflected from the paper at high angles of incidence as described in our copending Gloss meter application, and advantageously measured in units correspondingA to those in which gloss is measured and specied to the calendar department. Any deviation in the value of the gloss on the paper 'passing over roll I4. from that represented by the setting of slider 6T on slide wire 58 will therefore. result in an electric current through galvanometer 66; This current and the resulting deflection of the galvanometer from its zero position illustrated in Fig. 3 correspond in magnitude and direction to the magnitude and direction of the gloss deviation.

In a preferred. embodiment of our invention, 66 is a mirror galvanometer whose mirror is illuminated by a light 10 through a suitable lens 1l. When the galvanometer is undeected, the reected light beam takes the position shown in Figure 3. A plane glass plate 12 is interposed in the path. of the reected light beam. This plate reflects a part of the beam onto a screen 13 which is visible. to the operator (see also are; included .ixr-A theepanels; and boxes designated'h Figure 1.) When the galvanometer is undeflected, the reected beam falls on a clear space in the center of this screen. When the galvanometer reading changes in either direction, the light beam shifts to the right or left on this screen. A shift greater than a predetermined amount throws the beam through a band of one color 13-H on the one side, indicating too high a degree of gloss, or a band of another color 13-L on the other side, indicating too low a degree of gloss.

The means by which the detected changes in gloss variably adjust the calender pressure will now be described, The part of the light beam from galvanometer 66 which passes through glass plate 12 strikes a photoelectric cell 14 whenever it travels to a degree which indicates that the gloss is above a predetermined upper limit, and strikes a photoelectric cell whenever it travels in the other direction to a degree which indicates that the gloss is below a predetermined lower limit.

When the gloss is too high and this light beam consequently falls on photoelectric cell 14 it acts through an amplifier 1B to operate relay 11 which as hereinafter described closes a circuit to cause the valve operating motor 33 to rotate in a direction to decrease the calender pressure. When the gloss is too low and the light beam consequently falls on photoelectric cell 15 it acts through an amplifier 18 to operate relay 19 which, similarly, closes a circuit to cause the motor 33 to rotate in a direction to increase the calender pressure. In the arrangement illustrated in Figure 3, the position of the photoelectric cells or of screens adapted to shield them from the light beam, are preferably made adjustable as for example, by means of adjusting screws 1li- A and 15--A, so that the neutral zone, or range of permissible variation, between them may be adjusted to any width required to give the desired closeness of control. The upper limit of gloss above which the light beam falls on cell 14 and causes a reduction in calender pressure, and the lower limit of gloss below which the light beam falls on cell 15 and causes an increase in calender pressure, are not the limits of tolerance within which the gloss of the finished paper is to be held, but are somewhat closer to the set value of gloss, so that the light beam falling on cell 14 or 15 has opportunity to correct the deviation from the set value before it becomes great enough to be objectionable. Thus the term "permissible range as used in this specification and the appended claims means the range of gloss variation within which the corrective mechanism does not function, and should be clearly distinguished from the considerably broader range of gloss variation which is permitted on acceptable paper.

The limits of galvanometer deflection are so fixed that the light beam cannot travel beyond the outer limits of cells 14 and 15. This means that however great the deviation from standard gloss, the controls will always function to correct it unless intentionally turned oi.

Although normally the devices as described function to maintain a uniform gloss on the paper being produced, within predetermined limits, it is possible for the operator to disconnect the control means by means of a switch as hereinafter described, or, while leaving the control means operative, to release the calender pressure by turning valve handle 36 to the off position. This is frequently done by the opera- CROSS KH' UXLNUL- tors to facilitate operation when starting, stopping, in the vicinity of splices, etc., and results in the production of a section of paper web having an excessively low gloss at these times. Unless extreme care is used, some of this low gloss paper may be included with the good paper delivered to the customer. In order to prevent this, an additional photoelectric cell 8| may be located so that as soon as the gloss falls below a predetermined value, lower than that at which light falls on cell 15 to close relay 19, light falls on cell 8| which acts through an amplifier 82 and coil 83 to operate a marking device 84 (see also Figures 1 and 2). The device 84 unmistakably and conspicuously marks all paper of unacceptably low gloss, which is then readily discovered and removed before delivery of the finished paper. In cases in which the functioning of the gloss responsive control mechanism is prevented in the manner described, a decrease in gloss from the correct value causes a galvanometer deflection which increases from zero so that the light beam first falls on cell 15 and then reaches cell 8| when the gloss reaches a predetermined low limit. The cell 8| or a screen adapted to shield part of the cell from the light beam is preferably adjustable, as for example, by an adjusting screw 8|A, to permit adjustment of the low limit of gloss. It should be noted that the illustration in Figure 3 is purely diagrammatic and cell 8| is shown in a position to indicate the relative deflections required to cause the light to fall on cells 15 and 8|. In practice, the cell 8| is so disposed that light can fall on both of the cells 15 and 8| simultaneously. If desired, another photoelectric cell can be used to cause the paper to be marked wherever the gloss is above a predetermined upper limit. There is however, relatively little danger of this defect and in most cases, the marking of low gloss paper is all that is required.

Further reference to Figure 3 will show how the previously described relays 11 and 19 function to control the energization and direction of rotation of the pressure control motor 33. The motor 33 is connected to a power source, advantageously a three phase alternating current line, designated a. g. h. ln the drawings (see also Figure 1) through the reversing switches |0| and |02, operated by electromagnetic coils |03 and |04 respectively. An interlock shown diagrammatically at |05 prevents the closing of either switch when the other is closed.

The adjustment of the calender pressure in accordance with changes in gloss is made operative by throwing the control switch |20 (see also Figure 1) to the on position. Switch 2 which is operated by the valve handle 36 (as ndicated diagrammatically in Figure 1) which throws the hydraulic pressure on or off, then serves to direct the current through green lamp |22 (which indicates that both switch |20 and switch |2| are on so that gloss responsive control will function) or through red lamp |23 which indicates that gloss responsive control will not function. An interrupter switch |25 which must also be closed in order that the gloss responsive control may function will be hereinafter fully described and may for the present be considered to be closed.

Assuming that switches 20 and |2| are in the on position and the degree of gloss is too low, the light beam reflected from the galvanometer mirror strikes photoelectric cell 15 and thereby causes the closing of relay 19. Under these contlltions current from line wire'h 'passes through :switch |20, wire c,.and switch |2| to junction |26. From this point, it passes through green light |22, which indicates that the gloss responsive control is in operation, to line wire a. From junction |26, current also passes through wire b, and interl:runter switch |25 (here assumed to be closed), closed contacts of relay 19, Wire i, coil |03, wire e .and closed high limit switches ||2 and ||3 (the .operation of which will be hereinafter described) to line wire a. This energization of coil |03 closes fswitch and thus causes the motor 33 to rotate .in a direction to effect an increase in the calender .-pressure. 1f the degree of gloss is too high, the light beam reected from the galvanometer mirror :strikes photoelectric cell 14 and thereby closes .relay In this case, green light |22 remains :lighted and current from junction |26 ows @through wire b and interrupter switch |25, closed .contacts of relay '|1, wire i, coil |04, wire f, and flow limit switches and H6 (normally closed =as hereinafter described) to line wire a. This .energization of coil |04 closes switch |02 and causes the motor 33 to rotate in a direction to effect a decrease in calender pressure.

Means may also be provided for adjusting the :calender roll pressure manually, and such means is illustrated in Figure 3 as push button switches Il and ||4, also shown on the control panel ||0 ,in Figure 1. These manually operable switches are respectively connected to energize the coils .|03 and |04 of the motor energizing switches |0| -and |02, through circuits clearly shown in Figure :3. I'Ihe motor switch operating coil energizing circuits of the bush button switches and ||4 -respectively include the high limit switches ||2, r.||3, and the low limit switches ||5, IIS. All of Lthese limit switches are normally closed, and are .opened under certain circumstances, as explained below.

Overadjustment of either of the valves 23 and 1:24 in either direction might damage the mecha- `nism as described in said copending application -entitled Hydraulic calender and as diagram- :matically indicated in Figure l., where it appears that the valve adjusting shafts 4| and 42 are v:threaded to cause adjusting nuts 43 and 44 .to travel away from each other to increase the calender pressure. In order to prevent such damage -high limit switches ||3 and ||2 are arranged, as Atliagrammatically indicated in Figure l, to ybe opened by the nuts 43 and 44 respectively reaching the upper limit of their respective adjustments. As shown in Figure 3, the opening of Jeither or both of these switches will break the -circuit through relay '|9 or push button and =thereby deenergize coil |03 and permit switch |0| to open and stop operation of motor 33 and upward adjustment of valves 23 and 24. In order =to prevent damage by overadjustment of nuts 43 Land A44 towards each other to decrease the cal- 'ender pressure, low limit switches ||5 and ||6 are similarly arranged to be opened by the nuts :43 and 44 respectively reaching the lower limits .of their respective adjustments. Similarly theL opening of either or both of these switches will :break the circuit through relay-11 or push button `||4 and thereby deenergize coil |04 and permit vswitch |02 to open and stop operation of motor 33 :and downward adjustment of valves 23 and 24.-

fes

valve structure .should be desired to protect the .'calender, or for any otherreason.

The .apparatus described above serves to in- ,crease the calender pressure .and thereby to in- .crease the gloss 'being imparted to the paper when this gloss is too.low, and to decrease Vthe calender pressure and thereby to decrease the Agloss being imparted to the paper :when this gloss is too high, and will leave the calender pressure unchanged when the gloss is between predetermined limits. The full change of calender pressure is not reected as a change of gloss on the ,paperpassing over roll |4 (Figure 1) until that part of the paper web which was just entering the 4i'rst calender nip when the pressure change was completed has passed through the calender land onto roll I4. Accordingly, an appreciable ,time interval elapses during which the gloss on the issuing paper web at roll |4 remains toolowregardless of an adequate increase in calender pressure, or too high regardless of anadequate decrease in calender pressure. During this time the change in pressure would continue Whether or not further change in thatA direction were required. To prevent the phenomenon known as "hunting itis necessary that the pressurechange during this time shall not be so Vgreat as to carry the gloss across the neutral zone or permissible range and thus make an adjustment in the opposite direction necessary as soon as the .full effect of the Aadjustment is ,registered on the glossmeter.

This can be accomplished by establishing a suitable relation between the speed of adjustment and the speed of the paper .through the calender, so that the time required for the paper to pass from the iirstnip of thecalender to the glossmeter over roll |4 isless than the time .required for the .adjusting mechanism .to change the gloss through the neutral zone, or permissible range. For this purpose, an adequate speed reduction between motor 33 and va.1ves.23 and 24 may be used,

,or the valves may be operated rapidly, to secure a prompt corrective change in gloss, and this rapid operation periodicallyinterrupted for time intervals of such predetermined frequency and duration that the gloss responsivedevices will have opportunity to stop further pressure change Abefore the adjustmenthas been carried entirely across the neutral zone, and adjustment in the opposite direction is required. The paper speeds Yon which these speeds or time intervals are based .are advantageously `the normal or operating speeds of the calender and not the;slow threading inW speeds sometimes used.

This `periodic V interruption may be accomplished by a switch |25vwhich is advantageously of a sealed mercury type and may advantageously be operated byma cam |21 driven by a clockwork |28, which may be driven by a spring or a synchronous-clockrmotor, through the medium of cam follower |29 to which theswitch |25 is attached as indicated diagrammatically in Figure .3. VThe time fon and ,oi and the entire cycle are advantageously adjustable so ,they may be .regulated in conformity 4with the speed of paper travel land the distance through the machine to the glossmeter.

From the foregoingV description it is apparent .that the calender pressure may he increased or decreased manually (by push buttons Aand .|.|4) regardless .of lwhether.or not the pressure valve handle 36 .and therewith `switch |2| lare on or off and regardless .of whether the gloss ,responsive control .switch |20 `is on or off except that with the control switch on and the motor 33 running under control of the gloss responsive devices, interlock will prevent manual control from stopping or reversing the direction of its operation until its operation is stopped by the opening of switch |25 or by a change of gloss acting through the gloss responsive control pressure on either side of the calender stack without undue interference with the gloss responsive control system. With the switch |20 oi" and pressure switch |2| on, it is possible to operate entirely with manual control if desired.

While operating with the control switch |20 on it is possible by means of valve control handie 36 to release the pressure for threading or other purpose, thus throwing the green light oi and red light on and disconnecting gloss responsive control. When the pressure is again thrown on, gloss responsive control is resumed with the pressure unchanged from its previous value, the variations in gloss which may have occurred during the threading, etc., due to the release of pressure or other cause, having been unable to effect the operation of motor 33 while switch |2| is in the ofi position due to throwing the valve control handle 36 to the ou position.

The mode of operation will now be described. Assume it is required to produce paper having gloss of a specified value. The gloss responsive mechanism is first calibrated by taking a standard sample having a known value of gloss (defined as hereinbefore described), Wrapping this sample around roll I4 (Figures 1 and 2), setting the slider 61 on slide wire 68 by means of knob 69 to the known gloss value of the standard sample, then adjusting resistance 52 to vary the intensity of light source 5| until the line of light on screen 13 is in the center of the clear space between the two colored areas. In order to facilitate the detection of slight variations in light intensity from the standard value so determined, the rheostat 51 (see Figure 1) is adjusted until microammeter 56 indicates a selected even value, advantageously at the center of the scale, for the output of cell 55. During the subsequent operation of the device, any departure of the microammeter reading from this standard value is immediately corrected by readjusting rheostat 52 to correct the intensity of light source 5|. If the gloss on the calibration sheet used is different from that required on the paper to be calendered, the slider 61 is moved by turning knob 69 until the scale of the slide wire 68 indicates the required gloss value.

Control switch |20 is then turned to the on position, the paper is threaded through the calender in the usual manner, operation is started, and the pressure valve handle 36 is moved to the on position, which applies the pressure to the calender and throws switch |2| to the on position, extinguishes the red light |23 and lights the green light |22, indicating that the gloss responsive control is functioning. If the gloss, at the start, is much too low, galvanometer 66 will deflect to throw the light beam onto a colored part 13--L of screen 13 and onto photoelectric cells 15 and 8|. Light on the latter will cause marker 84 to deface the sheet to show that it is to be rejected. At the same time, cell 15 will cause the closing of relay 19 which acts as described to close switch |0| and operate motor 33 intermittently under control of interrupter switch |25 to increase the calender pressure and consequently the gloss on the paper.

As soon as the gloss on the paper reaches an acceptable value, the galvanometer deflection de- UHU nur www..

creases so that light no longer falls on cell 6I, marker 84 is released and the paper is no longer marked for rejection. In the meantime, motor 33 continues to increase the pressure until galvanometer 66 no longer reflects light onto cell 15, but between cells 14 and 15. Relay 19 is then released, switch |0| opens, and rnotor 33 stops, the pressure having reached the correct adjustment. The line of light is then in the clear space in the center of screen 13, indicating a correct value of gloss. If now the characteristics of the paper entering the calender change so that it is harder to finish, the light moves onto one of the colored areas 13-L on screen 13, light again falls on cell 15 and the adjustment described is repeated. If on the other hand the characteristics of the paper change in the other direction so that 'the gloss becomes higher, light falls on area 'I3-H and on cell 14. This immediately closes relay 11 which acts as described to close switch |02 which operates motor 33 in a direction to decrease the calender pressure and prevent too great a gloss from being imparted to the paper.

In case of a splice or tear out, etc., in the paper which, in the operators opinion, may cause a break if run through the calender at full speed and pressure, he first reduces the speed, and the control mechanism alters the pressure if necessary to maintain the proper degree of gloss. Before the splice or other defect enters the calender, the operator usually throws valve handle 36 to the off position which removes pressure from the calender and throws switch |2| to the off position extinguishing green light |22 and lighting red light |23 which indicates that the gloss responsive control is out of operation. The removal of the pressure soon results in a decreased gloss which causes deflection of galvanometer 66 to throw the light beam first onto cell 15 which closes relay 19, but because switch |2| is open, coil |03 is not energized and switch |0| is not closed so that no change is made in the pressure adjustment. Light reflected by galvanometer 66 also falls on cell 6| causing the paper to be marked as below standard until the splice or other defect has passed through and gloss responsive control restored by throwing valve lever 36 and consequently switch |2| back to the on position. This restores the pressure to its last adjusted value which, unless the raw stock characteristics have changed, will be the value required to impart the correct degree of gloss to the paper.

1n case the characteristics of the paper entering the calender change to a great degree, for example, if the stock becomes so hard that it will not take the required gloss with the maximum pressure available, the pressure setting of the valves 23 and 24 is raised in the manner just described until at least one of these valves reaches the upper limit of its adjustment. When this occurs the corresponding adjusting nut 43 or 44 contacts and opens corresponding high limit switch ||3 or ||2 as hereinbefore described thus preventing further operation of motor 33 in a direction to increase the pressure.V 1n such a case the gloss will be too low and will be so marked by marker 84 as described unless prevented by means such as hereinafter described. If, on the other hand, the lightest pressure available causes too high a gloss, one of limit switches |5 or I6 will be opened by contact with the corresponding adjusting nut 4| or 42 and will serve in the same manner to stop operation of motor 33, and prevent further adjustment which might damage LXammer fasiaio Y the mechanism. The operator can .then .usually correct this condition of excessive gloss by threading the paper through fewer nips in the calender.

With most grades of paper, the changes in pressure provided by the gloss responsive means of the invention constitute a very accurate and adequate control of the gloss. That is to say, the gloss responsive means used is able to detect and act upon much smaller differences in gloss than can be detected by the naked eye, and considerable changes in calender pressure are required in order to give relatively small changes in gloss. The mechanism of the invention is thus able to alter the pressure, as required to maintain the gloss well within the minimum visu-al requirements of uniformity.

At some times, due to unusual dryness of the paper or to other causes, such abnormally high calender pressures may be required to give the desired gloss to the paper that, if used, they would result in excessive wear and tear or other damage to the calender. The desired gloss can be secured under such circumstances by moistening the paper slightly before it enters the calender. Because, other things being equal, the more moist the paper surface, the higher will be the gloss imparted thereto by the calender, we find it advantageous to accomplish this moistening by a steam shower, or other moistening device, of known type connected with and controlled by the gloss responsive control means hereinbefore described.

Since it is only necessary to change the surface moisture to affect the gloss produced in the calender, the addition of moisture may take place immediately before the paper enters the calender and with this arrangement, the moisture may not have time to distribute itself throughout the thickness of the web prior to calendering.

In accordance with the present invention, this gloss responsive control of the application of moisture may be combined with the gloss responsive pressure control, hereinbefore described, to maintain a uniform standard value of gloss on the paper leaving the calender. This is advantageously accomplished by the electric circuits illustrated in Figures l and 3 by gearing a motor (designated at 333 in Figure 4, but which may be in this case the above described motor 33) both to a single steam valve mechanism 25| and to the duplex hydraulic valve mechanism 23-24. This modification is illustrated in Figure 4 which shows diagrammatically only the upper calender rolls 11 together with the entering paper web I3 below which is placed a steam shower 250 of known construction. The amount of moisture supplied to the paper through pipe 252 in the form of steam is controlled by valve 251. The opening of valve 251 is increased by the motor 333 when the gloss is too low, and decreased when the gloss is too high. This increase in the amount of steam applied to the paper takes place simultaneously with the increase in calender pressure hereinbefore described, and the decrease in steam applied takes place simultaneously with the decrease in calender pressure. A given amount of adjustment therefore has a greatly increased effect on the degree of gloss imparted to the paper so that the possible range of adjustment is greatly increased, though the sensitivity is decreased.

In place of a steam shower, known types of water sprays, similarly controlled, may be used in some cases though they are generally less satisfactory.

We can however, combine the moistening of the paper with the pressure adjustment in such a manner as to enormously broaden the range of gloss responsive control without impairing the sensitivity of the control. To accomplish this, we provide mechanism which operates to eiect changes in moisture content in response to changes in gloss characteristic only when gloss responsive changes in calender pressure are insumcient to correct the deviations in gloss from the required standard. 'I'his may be accomplshed, as shown in the disclosed embodiment, by employing the gloss responsive calender pressure control mechanism hereinbefore described, and, in connection with the limit switches 112, 113, and 116, providing valve motor controlling switches 312, 313, 315 and 316, as illustrated in Figure 5, so that when high limit switches 112 and 113 are opened, switches 312 and 313 respectively are closed, and when low limit switches 115 and 11 B are opened switches 315 and 316 respectively are closed. This operation of switches 312, 313, 315, and 316 may be accomplished in the same manner as the operation of pressure control switches 112, 113, 115, and 116, as shown in Fig. 1, by means of the sliding nuts 43 and 44. The corresponding switches may be mounted side by side so as to be contacted by the respective adjusting nut at the limit of its motion at substantially the same time. As shown in the figure. the pressure control switches are normally closed and adapted to open when contacted by nut 43 or 44. The steam valve motor control switches 312 313, 315, and 316, however, are normally open and adapted to be closed by contact with the nut 43 or 44. Since exact and dependable simultaneity of the closing of one of the switches 312, 313, 315, or 316, and the opening of its corresponding switch 112, 113, 115, or 116, may be diicult to secure and maintain in practical operation, and since when the pressure control switches open, the motion of the nuts 43 and 44 stops, it may be found desirable to set the steam control switches to close somewhat before the opening of the pressur control switches.

With this arrangement, the pressure control mechanism functions exactly as hereinbefore described until it is no longer suflicient to hold the gloss within the specified limits. When the pressure reaches its upper limit and still is not adequate to impart the requisite degree of gloss to the paper, at least one of the high limit switches 112 and 113 is automatically opened, as hereinbefore described, to prevent further operation of motor 33 in a direction to increase the pressure. At least one of the switches 312 and 313 is closed at the same time, or earlier if desired. As soon as one of these switches is closed, coil 383 is energized, closing switch 3111, which operates motor 333 to increase the opening of steam valve 251 land thereby increase the amount of steam supplied to the paper web entering the calender. As soon as the increasing moisture content of the paper has produced a sufficiently increased gloss, the gloss responsive means closes relay '11 and functions to decrease the calender pressure as described, the low limit switches |15 and 116 being closed at this time. The adjustment of the valves 23 and 24 to accomplish this decrease in pressure serves to close the high limit switches 112 and 1 13 and open switches 312 and 313 thereby stopping the operation of motor 333 and the resulting increase in the supply of steam to the paper. This steam supply then remains constant until more steam is required to give the specified gloss to the paper, when the operation described is repeated, or until in its gloss responsive downward adjustment the pressure reaches the lower limit fixed by the location of switches H and |l6 on valves 23 and 24. When this occurs, at least one of the low limit switches H5, H6 opens and prevents further decrease in pressure. At least one of the switches SI5, 316 has then been closed, energizing coil 304, thereby closing switch 302 which operates motor 333 in a direction to decrease the amount of steam supplied to the paper through valve 25|. With this arrangement, the pressure control functions as before and with the same degree of sensitivity to maintain a constant gloss on the paper being produced, and a change in the amount of steam being applied only takes place when the range of pressure variation is insufficient to compensate for the variations in the paper coming to the calender.

It will be understood that our devices can be considerably varied in construction and applica- .tion without departing from the present invention.

The potentiometer circuit illustrated and described, for measuring the output of the photoelectric cell responsive to the gloss. has been shown in a very simple form for purposes of illustration, and it will be readily understood that any desired refinements may be introduced without departing from the spirit of the present invention.

Although a potentiometer circuit is particularly advantageous for measuring the output of the photocell which is responsive to the gloss, other arrangements may be used for this purpose.

For example, a microammeter may be placed directly in the circuit with the photocell to measure its output. The indicating element is preferably a mirror which reflects the light beam from light 10 onto the photoelectric relays as above described and illustrated in Figure 3. With such an arrangement the microammeter will only be at zero when there is no light falling on the photoelectric cell 59. In order that the reflected light beam may be set 1n the center of the neutral zone between cells 14 and 15 and of the clear space on screen 13 at any desired value of gloss, the microammeter may be mounted on a concentric swivel with a calibrated scale reading in points of gloss Just as does the scale 58 (Figures 1 and 3). Any deviation from the gloss value to which the microammeter has been turned will function exactly as in case of the potentiometer to adjust the calender pressure to correct the gloss value.

In place of the mirror galvanometer 66 or the microammeter just described, it is possible to use an instrument of any suitable known type with an indicating hand in place of the mirror, and mechanical relays in place of the photoelectric relays illustrated and described.

Our invention, as hereinbefore described, will maintain a constant uniform degree of gloss on paper. Gloss is not only one of the most irnportant properties of paper, but the control of the manufacturing processes to give uniformity of gloss also serves to increase the uniformity of various other properties of paper, surface smoothness, density, etc., all of which go to make up the printing quality of paper. The use of our invention thus makes possible a greater uniformity of printing quality than has heretofore been available in commercial printing papers. with a corresponding increase in their value to the printer.

We claim:

1. Apparatus for producing paper having substantially uniform gloss which comprises in combination a calender, means including a motor for varying the gloss producing capacity of said calender, means including a photoelectric cell for detecting deviations from a predetermined value of the gloss on the paper as it passes from the calenderI and an automatic electric relay circuit controller electrically connected to said photoelectric cell and to said motor to operate said motor in response to variations in the output of said photoelectric cell to increase the gloss producing capacity of the calender when the gloss on the paper falls below said predetermined value and to decrease the gloss producing capacity of the calender when the gloss on the paper exceeds said predetermined value.

2. Apparatus for producing paper having substantially uniform gloss which comprises in combination a calender, an adjustable pressure controlling device for varying the pressure in said calender, a motor for adjusting said pressure controlling device, means including a photoelectric cell for detecting deviations from a predetermined value of the gloss on the paper as it passes from the calender, and an automatic electric relay circuit controller electrically connected to said photoelectric cell and to said motor to operate said motor in response to variations in the output of said photoelectric cell to increase the pressure in the calender when the gloss on the paper falls below said predetermined value and to decrease the pressure in the calender when the gloss on the paper exceeds said predetermined value.

3. Apparatus for producing paper having substantially uniform gloss which comprises in combination a calender, means including a motor and a uid control valve operated thereby for varying the surface moisture of the paper entering said calender, means including a photoelectric cell for detecting deviations from a predetermined value of the gloss on the paper as it passes from the calender, and an automatic electric relay circuit controller electrically connected to said photoelectric cell and to said motor to operate said motor in response to variations in 'the output of said photoelectric cell to increase the moisture on the surface of the paper entering the calender when the gloss on the paper falls below said predetermined value and to decrease the moisture on the surface of the paper entering the calender when the gloss on the paper exceeds said predetermined value.

4. Apparatus for producing paper having substantially uniform gloss which comprises in combination a calender, means including a motor for varying within predetermined limits the pressure applied to the paper by said calender, means including a second motor for varying the surface moisture of the paper entering said calender, means including a photoelectric cell for detecting deviations from a predetermined value of the gloss on the paper issuing from said calender, and a controller electrically connected to said photoelectric cell and to said motors to operate said first named motor in response to variations in the output of said photoelectric cell to increase the pressure applied to the paper by said calender when the gloss on the paper falls below said predetermined value and to decrease the pressure applied to the paper by said calender when the gloss on the paper increases above said predetermined value and to operate said second named motor to increase the surface moisture of the paper entering said calender only when the gloss on the paper falls below said predetermined value and the pressure applied to said paper has reached its maximum limit and to decrease the surface moisture of the paper only when the gloss on the paper increases above said predetermined value and the pressure applied to the paper has reached its minimum limit.

5. Apparatus for. producing paper having substantially uniform gloss, which comprises in combination a calender, an adjustable pressure controlling device, for varying the pressure in said calender, a motor for adjusting said pressure controlling device means and a fluid controlled valve operated thereby including a motor for varying the surface moisture of the web of paper entering the calender, means including a photoelectric cell for detecting deviations from a predetermined value of the gloss on the paper as it passes from the calender, and an automatic electric relay circuit controller electrically connected to said photoelectric cell and to said motors to operate said motors in response to variations in the output of said photoelectric cell and to so control the direction of operation of said -motors that said rst named motor will increase the calender pressure and said second named motor will increase the surface moisture of the paper web entering the calender when operated by said controller in response to detection of gloss below said predetermined value, and said first named motor will decrease the calender pressure and said second named motor will decrease the surface moisture of the paper web entering the calender when operated by said controller in response to detection of gloss above said predetermined value.

6. Apparatus for producing paper having substantially uniform gloss comprising in combination a calender, means including a motor for varying the pressure in said calender, means for projecting a beam of light at an angle against the surface of the moving paper web issuing from the calender, a photoelectric cell in the path of light from said source that is specularly reiiected from the surface of the moving paper web, and an automatic electric relay circuit controller electrically connected to said photoelectric cell and connected to govern the operation of said motor to cause said motor to increase the pressure in said calender when the intensity of said specularly reflected light is below a predetermined value and to cause said motor to decrease the pressure in said calender when the intensity of said specularly reflected light is above said predetermined value.

DONALD B. BRADNER. GEORGE C. MUNRO.

- A CERTIFICATE oF coRREcTIoN. A Patent No.,2,512,51o. March 2, 191g.

. DONALD B. DRAWER, ET AL.A

It is hereby-certified that error appears in the printed specification of the above numbered Datent'requiring 'corret-ion as follows: Page 5, second eolumn, line 5'6, for'"einander"A resid --calendr--g page 5, first column, 11n@ 55, for 'bush' read '-puqh; page 9, first column, line 15,. olaim 5, after the word *means* strike out "and a fluid controlled valve operated thereby' and insert the same afterl the word "motor"A in line 16, same claim; and that the said Letters Patent should be-read with this correction therein that the same may conform to the record of the casein the Patent Office. V I

signed and sealed this 20th any of -.Apr11, A. D; 19245.

Henry Van Arsdale, (Seal) Acting Commissioner'of Patents.,

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