US3203678A - Temperature control system for rolls - Google Patents

Description

w. c. SAWYER ETAL 3,203,678

TEMPERATURE CONTROL SYSTEM FOR ROLLS Filed May 1, 1965 22 24 {CORRECTIVE l8 |6 PYROMETER 20 I HIIHHIIIIIHIIIHIIIIIIII'IHIIIIIIIII IIHHIIIIPIIIIIIIIIIIIIIIII 3O INVENTORS WILLARD C. SAWYER BY GILBERT FORRESTER am a, W W

ATTORNEYS United States Patent TEMPERATURE CONTRGL SYSTEM FOR ROLLS Willard C. Sawyer, Westbrook, Maine, and Gilbert Forrester, Millicent, South Australia, Australia, assignors to S. 1). Warren Company, Boston, Mass, a corporation of Massachusetts Filed May 1, 1963, Ser. No. 277,297 8 Claims. (Cl. 263-6) This invention relates to a temperature control system for revolving rolls and more particularly to an apparatus for regulating the surface temperature of a cylindrical calendar roll such as is used in the paper-making industry. The invention will be described in connection with calenda rolls used in papermaking, but it is to be understood that the invention has broader application to any type of roll requiring heat regulation.

Calendering is a step in the paper-making process utilizing heavy polished cast iron rollers which are vertically stacked in a calender frame. The purpose of calendering is to flatten the web to a uniform thickness by passing it between the heavy rollers. Generally, the paper web has previously been dried by heat before coming to the calender. Thus, large amounts of heat are transferred to the calende rolls as the web is drawn through. The pape web is threaded, serpentine-fashion, around and between the calender rolls which revolve in alternately opposite directions forming flattening nips at their juncture lines. The web is drawn through the calender stack being progressively flattened at each nip.

It is very important in paper-making to control the temperatures along the length of the calender rolls Within close limits. The build-up of individual hot spots must be prevented at all times. If deviations in temperatures occur along the length of the rolls and continue uncorrected, variations in the thickness and quality of the paper web will result. The uneven thickness of the web is caused by areas of increased pressure occurring at the hot spots. The present invention comprises a new temperature control system capable of detecting these hot spots and directing a cooling means to these areas whereby a uniform temperature level is maintained across the roller and web surface. It should be understood that there is a strong correlation between the temperatures of the paper web and the rollers due to heat transfer which is constantly occurring. Therefore, the temperature sensing and the cooling functions can be applied to either the web or the rollers or a combination thereof with similar end results.

Therefore, one of the objects of this invention is to provide an effective temperature control system which will detect overall deviations from specified temperature limits occurring in a calender roll or paper web and institute corrective measures.

Anothe object is to provide a temperature control system which will detect and correct temperature deviations occurring in small defined areas on a roll or web.

A further object is to provide a temperature control system that employs a temperature-sensing device that in no way physically contacts the paper web or the calender roll.

A still further object is to provide a temperature control system that employs a temperature-sensing device which continuously traverses the calender roll or paper web seeking hot spots and causing a corrective air stream to be directed upon such spots to precisely maintain a uniform temperature across the entire surface of the calender roll or paper web.

Other objects and advantages of the invention will become apparent from a study of the accompanying drawings and descriptive matter in which is illustrated and described a preferred embodiment of the invention.

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The drawing represents a diagrammatic view of a temperature control system for rolls, showing a calender roll, a traversing pyrometer, and a corrective air source with directive nozzles having electrically operated valves.

Referring more particularly to the drawings, a calender roll 10 is shown with a journal 12 arranged to revolve within calender frame 14. The other calender rolls are not shown but are vertically stacked and constructed similarly. The paper web generally has a width slightly less than that of the calender rolls. It usually is drawn around the top roll and threads its way down through the stack. In this manner the paper web covers one-half of the surface of each roller (the top and bottom rolls may be covered a little more or a little less depending on the entry and exist directions taken by the paper web).

To provide sensitive heat detection, a heat-sensing device 16 is employed to scan the calender roll or web. This heat senser is located closely adjacent to, but in no way physically touching the surface of the roll or the web. In the preferred embodiment, the heat-sensing device is shown as a pyrometer. This instrument measures temperatures based on the heat energy radiated by the source (radiation pyrometer) The pyrometer utilized in this invention is preferably of the radiation type. Such pyrometers have an advantage over contact thermo-couple pyrometers in that no part of the pyrometer need come into direct contact with the hot body, and no part need be raised to a high temperature. This factor is important in the present invention because the pyrometer must be able to scan across adjacent web or roller surface areas without experiencing carry-over effects (hysteresis) Pyrometer 16 can measure temperature levels and be adjusted to close an interior electrical switch 17 upon detecting a temperature above a specified level. Furthermore, if desired, a pyrometer can be employed having two such switches, the other switch being closed upon observing a temperature below a specified temperature. Thus, hot (or cold) spots appearing in the calender oll or web can be detected whereupon the pyrometer will close an interior electrical switch. It should be noted that it makes no appreciable difference whether the pyrometer scans the surface of the calender roll or that of the web of paper since there is a direct temperature correlation between roll and web temperatures. In the illustrated embodiment, the pyromete is shown scanning the calender roll. A recording device is usually employed so that a continuous visual record of the temperature data is available.

Pyrometer 16 is movably mounted upon traversing conveyor 18 which is driven by motor 20. The function of conveyor 18 is to move pyrometer 16 along the length of the calender roll or paper web surface so that continuous temperature readings can be taken throughout the length of the roll or the web. In the preferred embodiment, the scanning run is made from right to left. Afte the pyrometer has completed its scanning run, conveyor 18 returns pyrometer 16 to its original position on the far right near motor 20 preparatory to the next scanning pass. Preferably no scanning is done during the return travel. The drawing shows four pyrometer scanning segments, designated on the calender roll 10 as A. B, C and D. The pyromete establishes a difierent electrical circuit as it moves from one scanning segment to another. Thus, the appropriate cooling apparatus can be selectively operated in response to the pyrometer findings in each particular scanning segment. The more scanning segments there are, the more sensitive the system will be to temperature deviations observed during the scanning run. The size of the calender roll or web and the degree of allowable temperature variation will determine the number of pyrometer scanning segments required. A scan- 3 ning segment length of about twelve inches has been found to be satisfactory under usual conditions. In all cases, the scanning is a continuous process in which the pyrometer is conveyed across the web or roll at a uniform rate.

The specific type of traversing means can assume a variety of forms. An endless chain conveyor can be used. A fishing reel guide type conveyor will function adequately. A reversing worm gear system may be satisfactorily employed. These examples point up but a few of the many possibilities.

A primary purpose of this invention is to detect hot spots on the calender roll or paper web and to direct cooling air on these spots. To accomplish this latter function, a corrective or cool air supply is provided such as an air compressor or blower 22. Air compressor 22 feeds into air line 24 which has multiple directional nozzles 26. In the embodiment shown in the drawing there are four nozzles which are positioned and arranged to direct cool air onto the calender roll surface. It has been found that the most accurate temperature control is achieved if the air jet is directed tangentially against the roll surface so that sidewise spread of the air stream is minimized. Another satisfactory but less preferred arrangement would be for the nozzles to be directed upon the web since the heat exchange process occurs from web to roll. There would normally be one directional nozzle 26 positioned opposite the midpoint of each scanning segment.

As previously stated, a paper-machine calender ordinarily contains several metal rolls stacked vertically in a frame. Paper being calendered thereon usually enters the stack near the top and leaves near the bottom. Thus the first transfer of heat from the web is to the top rolls of the calender. Heat is soon transmitted to the other rolls, however, so that hot spots on one roll develop corresponding hot spots on the other rolls. Hence the preferred location for the scanning device usually is at one of the bottom rolls of the calender. The cooling air can be directed at the roll scanned or at one or more of the other rolls as desired. Location of the scanning device at the calender makes possible the correction of uneven temperatures in the calender rolls due to peculiarities of the calender itself as well as those caused by uneven heat transmission from the paper web. A single scanning device on the calender can usually control the temperature across the width of the calender within 5 F. or less, which is normally as close as is requisite in most cases. If in special cases closer control is desirable, one or more additional scanning devices with accompanying cooling devices may be installed on other rolls in the calender.

It is also feasible to provide hot air nozzles in addition to the cool air nozzles opposite each scanning segment. This arrangement could be employed where it was desired to maintain an absolute mean temperature level in addition to the more common requirement of maintaining a uniform temperature level across the calender roll or web regardless of the absolute temperature level.

To regulate the passage of cool air through nozzles 26, valves 28 are provided in the throat of each nozzle. These valves can be of butterfly or other standard construction. Valves 28 are electrically operated and are preferably fitted with mechanical or electrical time delay elements (not shown). The time delays function after the valves have opened to cause the valves to remain open for a specified time period after which the valves reclose. The time delays are initially activated by the electrical current which causes valves 28 to open.

Pyrometer 16 has dual Wiper arm conductors 30 and 31 which extend from interior electrical switch 17. Conductor arm 30 is positioned to ride along power line contact strip 32 continuously in contact therewith. Conductor arm 31 is positioned to sequentially contact each of valve line contact strips 34-. Connecting electrical circuitry is provided to link each valve 28 into a separate circuit with pyrometer 16. Power supply 36 causes an electric current to flow in the affected circuit when that circuit is completed. This completion occurs when pyrometer 16 senses a temperature above the permissible level and closes its interior switch 17. Valve 28 then operates to allow cool air to be directed onto the affected segment of calender roll 10 or the paper web. The alternative embodiment employing hot and cool air sources, and nozzles requires a second electrical switch 17 adapted to close upon the detection of a temperature below a specified level with additional circuitry, valves and power supply to operate in response thereto.

Operation When a calender is started up after a prolonged idle period it will normally be at room temperature. As the calender runs its temperature gradually rises. During this period the pyrometer records the indicated temperatures. When the mean temperature has become reasonably stable, say after about 30 minutes of operation, the scanning device can be set to turn on the cooling stream at a determined level above the mean temperature. That level is herein referred to as the critical temperature level.

A cycle of the scanning procedure starts with pyrometer 16 located at the right hand extremity of conveyor 18. The pyrometer is conveyed toward the left, sensing the temperature of scanning segment A. Conductor arm 38 is continuously in contact with power line contact strip 32. Conductor arm 31 is initially in contact with the rightmost valve line contact strip 34. The pyrometer continuously reads the temperature level of scanning segment A of the calender roll (or the corresponding portion of the paper web). If the temperature anywhere within segment A exceeds the critical temperature which has been set into the pyrometer mechanism, pyrometer 16 closes its interior switch 17 which causes valve 28 in nozzle 26 on the opposite side of calender roll 10 to be activated. If the temperature reading is below the critical tempera ture level throughout segment A, switch 17 remains in an open condition.

If switch 17 is activated, valve 28 is opened and compressed air flows from air compressor 22 through air line 24 onto the surface of calender roll 10 (or onto the web). The electrical signal which activates valve 28 also energizes the valves time delay element which holds valve 28 in the open position for a set time period despite the subsequent breaking of the electrical circuit as the pyrometer proceeds leftward.

The pyrometer 16 continues its travel into scanning segment B. The previously described temperature reading, electric circuit completion upon the detection of a temperature above the critical limit, valve opening and air cooling are then repeated in accordance with the indicated temperature of the scanned area. Pyrometer 16 is conveyed leftward in this manner until it completes segment D. The pyrometer then is reconveyed by conveyor 18 in an inoperative condition to the rightmost starting position preparatory to a new scanning cycle.

The time delay element can be adjusted to hold valve 28 open for :a delay time of from zero seconds to the number of seconds required by the pyrometer to complete an entire scanning cycle. Thus, the valve opposite the scanning segment of the roll or web to be scanned has always reclosed by the time the pyrometer has reappeared for another reading.

Therefore, if a hot spot has been cooled below the critical temperature level by the time of a subsequent pyrometer scanning, interior switch 17 will be open and the valve will remain closed. If insufiicient cooling has occurred, the pyrometer will complete the circuit reopening the indicated valve and continuing the cooling stream upon the hot spot.

It will be observed that there may be any number of valves open at any one time during the scanning cycle.

Whereas the invention has been described by reference to a preferred embodiment and an alternative embodimerit thereof, it will be understood that numerous changes and modifications may be made therein without departing from the scope and spirit of the invention.

Having thus described our invention, we claim:

1. Apparatus for regulating the surface temperature of a cylindrical roll comprising: temperature sensing means adapted to be spaced from the surface of a cylindrical roll; control means responsive to said temperature sensing means for selectively passing a signal when the sensed temperature exceeds a given magnitude; traversing means adapted to laterally convey said temperature sensing means continuously across adjacent surface segments of the cylindrical roll; coolant dispensing means adapted to direct coolant onto the surface of the cylindrical roll, said coolant dispensing means including multiple valve-controlled nozzles each adapted to be laterally disposed opposite a cylindrical roll surface segmerit; and means for relaying signals passed by said control means to said valve-controlled nozzles for selective actuation thereof.

27 Apparatus for regulating the surface temperature of a cylindrical roll and a paper web comprising: temperature sensing means adapted to be spaced from the surface of a paper web; control means responsive to said temperature sensing means for selectively passing a signal when the sensed temperature exceeds a given magnitude; traversing means adapted to laterally convey said temperature sensing means continuously across adjacent segments of the paper web; coolant dispensing means adapted to direct coolant onto the surface of a cylindrical roll, said coolant dispensing means including multiple valve-controlled nozzles each adapted to be laterally disposed opposite a cylindrical roll surface segment; and means for relaying signals passed by said control means to said valve-controlled nozzles for selective actuation thereof.

3. Apparatus for regulating the surface temperature of a cylindrical calender roll comprising: a temperature sensing pyrometer adapted to be disposed in facing spaced relation with a calender roll surface, said pyrometer adapted to pass a signal upon sensing a temperature above a given magnitude; means for continuously conveying said pyrometer laterally across adjacent portions of the calender roll surface; a pressurized air reservoir; conduits adapted for directing the pressurized air upon portions of the calender roll surface; valves in said conduits for selectively permitting the flow of pressurized air therethrough, said valves being electrically connected to said pyrometer and individually responsive to a signal passed by said pyrometer whereby the apparatus directs pressurized air against those portions of a calender roll surface which have attained a temperature sufficient to cause said pyrometer to pass a signal.

4. Apparatus for regulating the temperature of a calender roll and a paper web comprising: a temperature sensing pyrometer adapted to be spaced from the surface of a paper web, said pyrometer adapted to pass an electrical signal upon sensing a temperature above a given magnitude; means for conveying said pyrometer laterally across adjacent portions of the paper web surface; means for directing coolant medium upon adjacent portions of the surface of a calender roll, valve means in said coolant directing means being electrically connected to said pyrometer and responsive to a signal passed by said pyrometer whereby the apparatus directs coolant medium against portions of the calender roll surface corresponding to portions of the paper web which have attained a temperature sufficient to cause said pyrometer to pass a signal.

5. Apparatus for regulating the surface temperature of a cylindrical roll comprising: a pressurized source of fluid coolant; means for directing fluid from said coolant source including a plurality of nozzles, each said nozzle adapted to be positioned opposite a determinate portion of the surface of a cylindrical roll and spaced therefrom; electrically operated valves in said nozzles for selectively controlling the flow of coolant therethrough; a temperature sensing pyrometer having switch means for passing an electrical current upon sensing a temperature above a preselected level, said pyrometer adapted to be spaced from the surface of the cylindrical roll in facing relationship; a plurality of independent open electrical circuits each including a power source and one of said electrically operated nozzle valves; means for continuously traversing said pyrometer across adjacent determinate portions of the cylindrical roll whereby each said independent open electrical circuit is sequentially contacted by said pyrometer switch means and whereby upon sensing a roll surface temperature above the preselected level, said pyrometer closes said switch means causing the valve in the contacted circuit to operate to allow coolant to pass onto the sensed determinate portion of the cylindrical roll surface.

6. Apparatus of claim 5 wherein said nozzle valves are adjustable to remain in an operative condition for a determinate period of time.

7. Apparatus for regulating the surface temperature of a cylindrical roll and a paper web comprising: tem perature sensing means adapted to be spaced from the surface of a paper web; control means responsive to said temperature sensing means for selectively passing a signal when the sensed temperature exceeds a given magnitude; traversing means adapted to laterally convey said temperature sensing means continuously across adjacent segments of the paper web; coolant dispensing means adapted to direct coolant onto the surface of the paper web, said coolant dispensing means including multiple valve-controlled nozzles each adapted to be laterally disposed opposite a paper web surface segment; and means for relaying signals passed by said control means to said valve-controlled nozzles for selective actuation thereof.

8. Apparatus for regulating the surface temperature of a cylindrical roll and a paper web comprising: temperature sensing means adapted to be spaced from the surface of a cylindrical roll; control means responsive to said temperature sensing means for selectively passing a signal when the sensed temperature exceeds a given magnitude; traversing means adapted to laterally convey said temperature sensing means continuously across adjacent surface segments of the cylindrical roll; coolant dispensing means adapted to direct coolant onto the surface of a paper web, said coolant dispensing means including multiple valve-controlled nozzles each adapted to be laterally disposed opposite a paper web surface segment; and means for relaying signals passed by said control means to said valve-controlled nozzles for selective actuation thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,721,729 10/55 Van Riper -64 2,793,006 5/57 Eaby 16589 3,033,539 5/62 Cook et al. 3454 CHARLES SUKALO, Primary Examiner.

Claims (1)

1. APPARATUS FOR REGULATING THE SURFACE TEMPERATURE OF A CYLINDRICAL ROLL COMPRISING: TEMPERATURE SENSING MEANS ADAPTED TO BER SPACED FROM THE SURFACE OF A CYLINDRICAL ROLL; CONTROL MEANS RESPONSIVE TO SAID TEMPERATURE SENSING MEANS FOR SELECTIVLELY PASSING A SIGNAL WHEN THE SENSED TEMPERATURE EXCEEDS A GIVEN MAGNITUDE; TRAVERSING MEANS ADAPTED TO LATERALLY CONVEY SAID TEMPERATURE SENSING MEANS CONTINUOUSLY ACROSS ADJACENT SURFACE SEGMENTS OF THE CYLINDRICAL ROLL; COOLANT DISPENSING MEANS ADAPTED TO DIRECT COOLANT ONTO THE SURFACE OF THE CYLINDRICAL ROLL, SAID COOLANT DISPENSING MEANS INCLUDING MULTIPLE VALVE-CONTROLLED NOZZLES EACH ADAPTED TO BE LATERALLY DISPOSED OPPOSITE A CYLINDRICAL ROLL SURFACE SEGMENT; AND MEANS FOR RELAYING SIGNALS PASSED BY SAID CONTROL MEANS TO SAID VALVE-CONTROLLED NOZZLES FOR SELECTIVE ACTUATION THEREOF.

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