Патент USA US2135627код для вставки
Nov. 8, 1938. H, J. SMITH _ 2,135,627 TEMPERATURE CONTROL FOR PAPER MILLS AND THE LIKE Filed June 24, 1955 a Sheets-Sheet 1 , INVEN R, ATTORNEY. NOV. 8, ‘1938. _ H, J, sMlTH 2,135,627 TEMPERATURE CONTROL FOP. PAPER MILLS AND THE LIKE Filed June 24, 1935 ' 3 $heets—$heet 2 / '3 4g .50 . Q a: 59‘ 'im a; %k S.‘ INVEKOR. ATTORNEY. Nov. 8, 1938. H, J, SWTH ’ 2,135,627 TEMPERATURE CONTROL FOR PAPER MILLS AND THE LIKE Filed June 24, 1935 ‘ 3 Sheets-Sheet 3 7 T m‘ . ‘(/1913 . I151 v g 424 121' ' i _ : 25a _ - 122 g ~~JZ7 [12g 160’? i I05 103 106 9? l0 a,‘ ‘ 107 10 o 0 ‘/@''Q 108 | I ' ‘L 409 | I 1&9 | I "1‘ ‘ 110 1/414 11 x _ _ 4 1147 ' 150 112 140 145 131 148 125 - >140 _ > 151 v - - 111' ,1 I ‘152 136‘ .129 < -_ _ . 130 ' 1'53 H_OV.A.C. % /WM ATTORNEY. Patented Nov. a, 1938 2,135,621 A UNITED STATES PATENT’ OFFICE‘ ' ausszr ram-saunas common roa Paras mans also m use I‘ Razor 1. Smith, Longmeadow, Mara, assignor, by mesne assignments, to General Motors Corpo ration, Detroit, Mich, a corporation of Dela ware . Application June 24-, 1935, Serial No. 28,056 “Claim. (CI. 34-48) \v This invention relates ‘to temperature¢control In accordance with the present invention, the systems, and more particularly to- a system for controlling the temperature of the drying rolls in paper mills and the like. _ ' movement of a steam supply valve by means of a reversible motor-control unit. In order to ' An object of the invention is to ‘provide an automatic control for the moisture content of the provide means for adjusting the "range of control 5 sheet which is discharged from the drying rolls changes in stock. a second motor-control unit is‘ provided which ‘is operated by a hand control or of a paper mill. Another object is to provide an'accurate and automatic system, controlled by variations in the moisture content of the sheet which is received by the drying rolls, for varying the temperature of the rolls so as to discharge the sheet with a uni _ form moisture content. i position of the tensioning roll is translated into I \. Another object is to provide a system of the above type which-maybe readily adjusted to ac commodate diiferent types of sheet, or stock hav ing different moisture contents. Another object is to provide .a system of the above type which is adapted to operate in con junction with present‘ equipment, whereby the ‘cost of installation is reduced to a minimum. Another object is to provide a system for main taining the rolls at a predetermined temperature of the motor-control unit in accordance with by an automatic thermostat. The ratio of con trol eifected by the first and second motor-control 10 units may be varied in order to provide the de sired result. The automatic thermostat may be controlled in accordance with the steam conden sate temperature at a selected roll, for the pur pose of maintaining the temperature of the rolls ll substantially uniform when the control of the first unit is interrupted, as, for example, in re sponse to a break in the sheet. Means is pro vided for manually connecting either the hand control or the thermostat into the circuit, as de sired. _ ' ' Other features of the invention consist in the various details of construction and combination during periods when no sheet is being received - of parts as hereinafter more fully set forth. The broader aspects of the invention will be thereby. better understood by referring to the following . Another object is to provide a simple, conven-' lent and dependable device of the type above in dicated. _ v ' Other objects will be apparent from the fol lowing description. 7 ~ able temperatures ' by heating means,- su‘ch as steam, and are adapted to discharge the sheet with a predetermined moisture content. A fea ture of the present invention consists in fstillsll ing the variations of moisture content of the in coming sheet to control the steam supplied to the rolls in such manner as to compensate for said variations. ._,, > ' description, taken in connection with the accom Danying drawings in which a preferred embodi ment has been disclosed for purposes of illus trationonly. _ ; In the drawings, The invention is primarily intended for use in connection with the drying rolls of a paper mill. In such mills the sheet is passed successively over a plurality of rolls which are maintained at suit ‘ » In one embodiment, the tension of the incom 5 ing sheet is used as a measure of the moisture content. A tensionlng roll, such, for example, as a Stickies roll, is held against the incoming sheet ' > ' Figure 1 is a ditic view of a temper ature-control system embodying the present in-' vention; . ‘ > Figure 2 is a‘ front elevation of the automatic control switch. ' ‘ ' -' Figure 3 is a side view thereof; I A ' Figure 4 is a detail view of the ‘automatic con trol mechanism; ' ‘ Figure 5 is a front’ elevation of the control 40 panel; ~ . Figure 8 is a wiring diagram showing the 6011-! nections of the signal lights; Figure 7 is a section of the indicating unit, taken along the'line ‘I-‘--‘l of Figure 8; ' Figure 8 is a side view of the indicating unit; and - - . in' such manner that the position of the roll is - determined by the moisture content of the sheet Figure 9 is a ‘wiring diagram showing the con nections between the‘ hand control; lautomatic 0 at any instant. Inasmuch as the tensioning roll is responsive to minor changes in moisture con: tent, means is provided to integrate the move ment of the roll so as to e?ect a control only in temperature control and motor-control unit. In the following description and in the claims, certain speci?c terms have been used for con venlence in referring to‘ the various details of the accordance with the average moisture content of . invention. These terms, however, are to be in terpreted as broadly as the art will permit. the sheet over predetermined intervals. 65 2 ~ 2,185,627 Referring to the drawings more in detail, the invention is shown in Figure l as applied to the drier of a paper mill which comprises a plu rality of rolls in over which a sheet H of paper is passed in the usual manner for successively drying the same as it passes over the rolls. The rolls may be heated by steam supplied from a header l2 and fed to the individual rolls l0 by communicatingpipes [3. The condensate from 10 each roll is collected in a well l4 and is removed through a pipe l5 which connects with a drain line it. Steam maybe supplied to the header ‘the pulley G2 and turns therewith. The contacts 58 are adapted to alternately engage contacts 1| carried by a contact arm 12 which is supported by a sleeve 13 journalled on the shaft 59. The ' contact arm 12 carries a pair of brushes 10 which are electrically connected, respectively, to the contacts 1| and are adapted to engage sets of » stationary contacts 14 and 15 which are mount ed on a stationary support 15. The construction is such that rotation of the pulley 62 in'one direction closes one pair of con tacts 58 and 1| and transmits a force there through to cause rotation of the contact arm ' l2 from a main- l1 having a control valve 20 12. Rotation of the pulley 62 in the opposite di which may be operated by a lever 2 l~ in accord ance with the automatic control mechanism to , rection breaks the ?rst-mentioned pair 01 con tacts 68 and 1!, closes the other pair of contacts be described. 68 and 1!, and causes rotation of the contact The lever 21 is controlled by a pair of motor control units 25 and 26 having arms 21 and 28 arm 12 in the opposite direction. The contacts 68 and 1| thus ‘constitute reversing contacts respectively which are connected by links 29 and 30 to a control lever 3|. The control lever 3i is to complete a circuit to one or the other of the 20 connected to the lever 2| by means of a link 32, brushes 10, depending upon the direction of ro tation of the pulley 52. The position of the the point of connection of the link 32 to the con trol lever 3i being varied by a slider 33 having a brushes 1!) determines the position of the mo~ hand set screw 34. By varying the position of tor-control unit 25 by a circuit, to be described. For limiting the movement of the pulley 62, the slider 33, the ratio of the control of the mo tor-control units 25 and 26 may be adjusted. a stop 11 is provided which is adapted to engage When one of the control units is stationary, the the belt 59 when the pulley 82 is moved to either link 29 or so which is connected thereto serves extreme position. A contact 18 may be carried by the stop 11 to engage one of a pair of con as a fulcrum about which the control lever 3| tacts 19 for closing the circuit to the signal 30 30 may pivot in response to movement of the other motor-control unit. In the form disclosed, the motor-control unit 26 operates as a master con lights, to be described. The various contacts 14 and 1.5 are connected trol for varying the operating range of the valve 20, whereas the motor-control unit 25 operates as an automatic control which is actuated in accordance with the moisture content of the incoming sheet. The control device for actuating the motor control unit 25 is shown more in detail in Figure 40 4. It comprises a tensioning roll 33 which is mounted upon an arm 39, pivoted as at 40, and held by a weight 4| against the sheet H of paper which is being supplied to the drying rolls. The by a cable 80 (Figure 1) to the motor-controb arm 39 is connected to a valve 42 which controls 45 the flow of ?uid, such as water, through a pipe stantaneous variations in the sheet. In so do ing, it causes the valve 42 to operate in a corre 43 leading to a cylinder 44. The cylinder 44 is provided with a discharge line 45 regulated by a valve 46. The cylinder 44 carries a piston 41, the position of which is determined by the 50 quantity of ?uid within the cylinder. The piston 41 carries a piston rod 48 which is connected to a belt 49 passing over pulleys 50 and 5| and having stops 52 and 53 adapted to engage the lever 2| for controlling the position 55 of said lever in accordance with the movement , of the belt 49. The spacing'between the stops 52 and 53 permits a certain amount of move ment of the belt 49 without actuating the lever 2!. Suitable weights 54 and 55 may be asso 60 ciated with the belt 48 for maintaining the same in operating condition and to determine the operating characteristics of the device. A belt 59 may also be connected to the piston rod 48, as by an» arm 50. Said belt 59 may be unit/25 in such manner that the arm 21 of the motor-control unit, is caused to take up a posi~ tion corresponding to the position of the brushes 10 on said contacts. In the operation of the control device illus trated in Figure 4, the tensioning roll 38 presses against the sheet I l and causes movement of the 40 arm 39, dependent upon the moisture content of the sheet. Innormal operation, the arm 39 is caused-to oscillate in accordance with the in sponding manner. If the valve 42 admits water to the cylinder“ at a rate equal to the rate of discharge of water through the discharge line 45, no movement of the piston 41 will take place. If the valve 42 admits water to the cylinder 44 at a rate in excess of or less than the rate of dis charge through the discharge line 45, the water level will rise or fall, respectively, in the cylin der 44 and will cause corresponding movement of the piston 41, which is transmitted by the belt 59 to the control switch 53. The control switch 63 actuates the motor-control unit 25 to progressively open or close the valve 20. The manner of connection is such that an in crease in the moisture content of the sheet II causes the valve 20 to be opened so as to supply additional steam to the rolls 10, whereby the temperature of said rolls is raised an amount pulley 52 of a control switch 53 which is adapt adapted to compensate for the extra moisture contained in the incoming sheet. If the moisture content of the incoming sheet decreases, a re ed, by its position, to determine the operating verse operation takes place, the piston 41 being 66 passed around a pulley GI and thence over a position of the motor-control unit 25. A weight 64 may be hung on the end of the belt 59 to 70 hold the same in frictional engagement with the pulley 52. The control switch 63 is shown more in detail in Figures 2 and 3 as comprising the pulley 82, over which the belt 59 passes, and a pair of con 76 tacts 68 mounted upon a shaft .59 which carries raised or lowered in accordance with the aver age opening of the valve 42 which, in turn, is determined by the average moisture content of the sheet H over a given interval. The contacts 19 may be connected to heating coils 82 which are associated with thermostatic switches 83. Each switch 83 is adapted to close a contact 84 to a signal light 85 which may be 45 , ' 2,185,627’ a mounted,,for example, on the control panel 86, gear. train I 26 from a pinion I26 carried by a as illustrated in Figure 5. The connection is‘ reversible motor I21. A plurality of sets of sta such that, when one of the contacts 19 is closed a su?icient length of time to actuate the switch 83, the signal light 85 is lighted so as to indicate to the operator that an extreme change is taking tionary contacts I28,‘ I29 and a contact I30 are mounted on a support I3I in position to engage‘ the commutator I23 as the commutator is rotated 5 bythe motor I21. _ The motor~control units 25 and 26 and the place. The switch 83, however, is su?iciently slow-acting as to prevent the signal light 85 from . indicating unit I20 maybe of similar construc tion with the exception of the indicator I2I, being energized in response to momentary clos .10 ing of the contacts 19. When the pulley 62 is moved to either of its extreme positions, the stop . 11 engages the belt 59 to limit the movement of which, in the case of the motor-control units 25 10 and 26, is” replaced by the arms 21 and 28. The units may, for example, be of the type described the pulley. If further movement of the piston in my copending application, above-mentioned. A suitable control‘ circuit for the indicating unit 41 takes place, the belt 59 slips about the periph 15 cry of the pulley 62. The stop 11 also provides ‘ . I20 is illustrated, for example, inv Figure 9, In 16 manual means for adjusting vthe pulley 62 with this ?gure, the reversible motor I21 is shown as > a reversible shaded pole motor having a ?eld respect to the belt 59. '20 The second motor-control unit 26 may be con nected to a hand switch 89 (Figure 1) or to an winding I32 which may constitute the secondary of the transformer I33, the primary I34 of which automatic thermostat 90, both of which may be may be connected to a source vof A. C. supply. The motor is provided with a pair of shading mounted upon the control panel 86. , The hand switch 89 may be of the type de ~' coils I35 whichuwhen energized, are adapted to scribed in my copending application Serial No. cause rotation of the motor in one direction, and 657,237, ?led February 17, 1933, for Control by another ‘pair of shading coils I36 which are 25 integration. It may comprise, for? example, a adapted to cause rotation ofv the motor in the shaft 9| (Figures 7, 8 and 9). carrying an arm 92 opposite direction. These coils I35 and I36 may having apair of contacts 93 adapted to engage be connected to a double-pole, double-throw contacts 94 mounted on a contact arm 95. The switch I31 having a set of poles I38 connected contact arm 95 is mounted for rotation on a 30 sleeve 96 which is journalled eccentrically about the shaft 9|. .A control handle 91 may be con nected to the shaft 9|. The contact arm 95 by leads I39 to the contadts 9a of the hand switch carries a pair of brushes 98, 99 which engage sets tacts II2 of the thermostat 90 maybe connected oi’ contacts I00, I0! in accordance with the posi 35 tion of the control handle 91. ' The contacts I00, IOI are connected to the motor-control unit 26 in the manner to be described. The thermostat 90 may be of the type shown in 0 my Patent No. 1,952,571, dated March 27, 1934. .40 It may comprise, for example, an ‘arm I 03_piv oted, as at I04, and actuated by any expansible bellows I05 in accordance with the temperature of the ?uid therein. A spring I06 may be used ' to adjust the operating range of the thermo 89 and a set of poles I40 connected by leads I“ to the contacts I01 of the thermostat 90. The contacts I00 of the hand switch 89 and the con by cables I45 and I46, respectively, to a junction box I41 which is connected by a cable I48 to the ; contacts I28 of the indicator unit I20. The con tacts IOI of the hand switch 89 and the contacts II 3 of the thermostat 90 may be connected by cables I49 and I50, respectively, to a junction box. I5I which is connected by a cable I52 to the con- i . tacts I29 of the indicatorunit I20; ‘The contact I30 of the indicator unit I20 is connected by a line I53 to the field winding ‘I32 of the motor I21. The above connections are such that when the switch I31 is in one position, the hand-control stat. The arm I03 carries a pair of contacts I 01 which are adapted to engage contacts I08 car riedon a contact arm I09 which is pivoted, as at H0, to the arm I03. The contact arm I09 carries a pair of brushes III which are adapted to engage sets of contacts II 2 and H3. The con tacts I I2 and I I3 may be connected to the motor control unit 26 in the manner to be described, switch 89 is connected in the circuit. If then the handle 91 is turned in one direction, for ex ample, in' a counter-clockwise direction, as viewed in Figure 9, the pair of contacts 93 and. 94 at the left is closed, thereby completing the circuit from I the shading coils I35>through the switch I 31 and one lead I39 to the selected contacts 93 and 94, whereby, the motor-control unit may be operated in accordance with the position of the thermo thence to the brush 98, one of the contacts I 00, through the cables I45 and I48 to one of the stat. ‘ . The bellows I05 may be connected by a ?exible tube II4 to a bulb II5 which may be mounted in a suitable well in the return condensate line of one of the rolls I0.‘ The thermostat accordingly 60 is responsive to the temperature of the steam contacts I28, thence through vthe commutator I23, the contact I30 and the return line I 53 to the ?eld winding I32 of the motor I21. The mo tor is then caused to operate in agiven direction ' until the circuit is broken. by the commutator I23 leaving the contact I28 which is energized at that moment.‘ If the handle 91 is moved in , I49, I52 to a contact I29 and energizing the op- 5 condensate in the selected roll I0 and is adapted to actuate the motor-control unit 26 so as to', the opposite direction, the opposite pair of cone tacts 93, 94 is ‘closed, thereby completing a cir control the steam supplied to the roll in-a man cuit through the brush 99, a contact I III, cables ner adapted to maintain the roll at a predeter mined temperature. In order to indicate to the operator the posi - posite coils I36, which causes a reverse move-‘ ' tion of the motor-control unit 26, an indicating ment of the motor until the commutator I23 unit I20 is provided (Figures 5, '1 and 8) having breaks contact with‘ the contact I29" which is an indicator I2I moving over a scalell9, cali , vbrated to show the angular position of the arms 28 of the motor-control unit 26. This indicat ing unit I20 may comprise a‘shaft I22 carrying the indicator I2I. A commutator I23 and a worm gear I24 mayvalso be connected to the shaft I22. 75 The worm gear I24 may be driven through a energized at that moment. The motor I 21 is thus reversibly and progressively operated in ac- ‘(0 cordance with the position) of the handle 91. The contacts I28 and I29 may be relatively dis- I placed to provide di?erent positions of the motor- I control unit in‘opening and closing the valve 20. I When the switch I31 is thrown into the oppo- 76 4 2,135,627 site position, the hand-control switch 89 is dis connected and the thermostat 90 is connected in the thermostat 90 to the motor-control unit 26. The thermostat 90 is adjusted to actuate the the circuit. The control of the motor I21 by the thermostat 96 is then the same as that above motor-control unit 26 so as to maintain the rolls described in connection with the hand switch, the motor being reversibly and progressively actu ated in response to temperature variations regis tered by the thermostat 90. It is to be understood that the connections be 10 tween the contacts 14 and ‘I5 of the control switch 63, and the motor-control unit 25 are similar to those above described. This connec tion is illustrated in Figure 1 as comprising a cable 80 connecting the control device 63 with 15 the motor-control unit 25. It is also to be noted that the motor-control unit 26 and the indicat ing unit I20 are connected in parallel so that the indicator I2I shows at all times the position of the motor-control unit 26. The switch I3‘! 20 is connected to a junction box I55 which is con nected in parallel by cables I56 and I51, respec tively, to the motor-control unit 26 and the indi cating unit I20. The switch I31 may be operated by a handle I58 mounted upon the control panel 86. The control panel may also carry a suitable temperature recorder I59, a steam pressure re corder I66 and a chart IBI. In the operation of this system, the handle I58 is normally in a position such that the hand control switch 89 is connected in circuit, whereby the position of the motor-control unit 26 and the indicator unit I20 are governed by the position of the handle 91. Assuming a paper having'pre determined characteristics to be passing over the various rolls ID, the tensioning roll 38 will take up a position depending upon the moisture con tent of the paper, thereby causing the piston 41 and the belts 49 and 59 to take up corresponding positions. The motor-control unit 26 is then actuated by manipulation of the handle 91 so as to bring the lever 2! into engagement with the stop 53 of the belt 49, whereby the control of the steam supply is taken by the belt 49. The stop 'I'I of the control switch 63 is then adjusted to 45 the central position by causing the pulley 62 to slip with respect to the belt 59. Thereafter, the steam supply will be under the control of the tensioning roll 38 and the motor-control unit 25. Said unit operates to produce minor variations 50 in the steam supply in accordance with the in stantaneous positions of the control switch 63 caused by changes in the average moisture con— tent of the sheet. If the moisture content of the sheet changes 55 suddenly or becomes such that the control switch 63 is actuated to the limit of its'movement, there by closing one of the contacts ‘I9, one of the in dicating lights 85 on the panel 86 will be ener gized to indicate to the operator that a change is taking place. If the control device does not soon correct the change, the operator may make suitable manual adjustment of the steam supply by actuation of the handle 91 of the hand switch 89. The hand switch 89 is also used when the stock is changed and to adapt the system for use with different grades of paper. In the event of a break or between runs when no sheet is passed over the rolls I0, the control device 63 becomes inoperative. It may be desired 70 to maintain the temperature of the rolls I0 sub-, stantially constant during this period so that the rolls will be ready for use when a sheet is again supplied thereto. For this purpose, the lever I58 is thrown to the opposite ‘position, thereby dis 75 connecting the hand switch 89 and connecting I0 at a predetermined temperature. When changing from the thermostat control to the hand switch, it is necessary to know the position of the motor-control unit 26 in order to make a corresponding setting of the hand switch. The indicating unit I20 is used for this purpose, since it operates in conjunction with the motor 10 control unit 26 and shows at all times the posi tion thereof. It is obvious, however, that this unit may be omitted if such indication is not required in any particular instance. It will be noted that the above device is adapted 15 to maintain the drying rolls at suitable tempera tures to stabilize the moisture content of the ?n ished sheet. In certain instances, the moisture readings were stabilized with a variation of 0.2%. The device also permits the rapid change-over between different types of stock and eliminates waste due to improperly dried paper or due to breaks which are often caused by faulty drying. The adjustments are such that they may be read ily adapted to any desired operating conditions, and the controls are arranged on a panel suited to give a visible record of the operation of the system. The position-indicating unit I20 shows at all times the position of the motor-control unit 26. After a paper break or on change of orders, the operator sees instantly just where to position the handle 91 to pick up where the thermostat leaves off. Under the close control herein provided, it is possible to readjust the distribution of heat in the various rolls and to provide for balanced paper ‘shrinkage across the mill, thereby reducing the breaks and improving the general quality of the paper. The ability to maintain a uniform and 40 correct drying roll temperature with proper dis tribution of the shrinkage across the whole mill permits increasing the speed, and therefore the tonnage, up to the limit of capacity of the mill. The hand switch 89 may constitute a master control for adjusting the system for different pa pers. The master control can position the valve in any one of twelve positions. The control switch 63 can position the valve in twenty-six different positions. The relative control can be 50 adjusted by varying the position of the slider 33 on the control lever 3I. It is to be noted, there fore, that an extremely accurate control is ef fected. . The signal lights 85 may, for example, com 55 'prise red and green lights, and are adapted to call the operator’s attention to the fact that the sheet is too wet or too dry and that connection at the master control is required. Although a preferred embodiment has been dis 60 closed for purposes of illustration, it is evident that various changes and modi?cations may be made therein without departing from the scope of the invention, which is to be limited only in accordance with the following claims when inter preted in view of the prior art. I claim: 1. A temperature-control device for paper mill drying rolls over which a sheet of paper is passed to be dried comprising, in combination, a source 70 of heat supply to said rolls, a valve adapted to control said supply, a pair of reversible motor control units adapted to jointly control the posi tion of said valve, means responsive to variations in tension of the sheet due to variations in mois 2,135,027 ture content thereof to actuate one of said units, 'a hand control, means responsive to the roll tem perature, and means to actuate the second unit by either said hand-control or said temperature _ 5 sheet to automatically actuate one ot'said units ‘ and a second control means adapted to actuate the other of said units. ‘1 ‘ - drying rolls over which a sheet of paper is passed to be dried comprising, in combination, a source 7. A temperature-control device for paper mill drying rolls over which va sheet of paper is passed“ to be dried comprising, in combination, a source of heat supply to said ‘rolls, a valve adapted to control said supply,'a-pair of reversible motor of heat supply to said rolls, a valve adapted to control units adapted to jointly control the posi responsive means. ' 2. A temperature-control device for paper‘mill 10 control said supply, a pair of reversible motor _control units adapted to jointly control the posi tion of said valve, means responsive to variations in tension of the sheet due to variations in mois ture content thereof’ to actuate one of said units, a hand control, means responsive to the roll tem perature, means to actuate the second unit by either said , hand-control or said temperature responsive meanshand an indicator unit adapted to indicatev the position of said second unit so as 20 to assist the operator in making manual adjust ments‘by said hand control. 3. A device for controlling ,the temperature of drying rolls over which a sheet of paper is passed to be dried, which comprises means responsive to . tions in moisture content thereof, a progressive successive multi-step reversible switch actuated by said means, a reversible motor-control unit actuated in accordance with the movement of said 30 switch, a source of heat supply to said rolls, means actuated by said unit to control progressively said supply, means to limit the movement of said switch, a pair of signal circuits, and means oper able when the switch remains in its‘ respective .35 limit positions for a, given time to energize said circuits. 4. A device for controlling the temperature of drying rolls over which a sheet of paper is passed to be dried, which comprises means responsive 40 to variations in tension of said sheet due to varia tions in moisture content thereof, a progressive reversible switch actuated by said means, a' re versible motor-control unit actuated in accord vance with the movement of said switch, a source 45 of heat supply to said rolls, means actuated by said unit to control progressively said supply,‘ .means to limit the movement of said switch, a , pair of signal circuits, thermostatic switches to control said circuits, a heating ‘resistance asso 50 ciated with each of said thermostatic switches, and means to energize said heating resistances when said reversible switch is at the respective _ 5. A device for controlling the temperature of drying rolls over which a‘ sheet of paper is passed to be dried, which comprises a member adapted to press against-the sheet for tensioning the same, a fluid cylinder, means responsive to movement of said member to control "the supply of ?uid to said cylinder, a piston actuated by said ?uid, a ‘--'progressive reversible control switch actuated by movement of said piston, a reversible motor con trol unit actuated in accordance with said control switch, a source of heat for said rolls, and means actuated by said motor-control unit to control said source. , _~ I 8- Atemperature-controlfdevice for paper mill 15 drying rolls over which a sheet of paper is passed to be dried comprising, in combination, a source of heat supply to said rolls, a valve adapted to control said supply‘. a pair of reversible motor control units adapted to jointly control the posi ' 6. A temperature ‘control device for paper mill drying rolls over which a sheet of paper is passed to be dried comprising, in combination, a source 70 of heat supply to said rolls, a valve adapted to control said supply, a pair of motor-control units, a variable ratio linkage connectingrsaid units to said valve wherebythe ratio of control effected by the respective units may be adjusted, means re 75 sponsive to variations in moisture content of said 20. tion of said valve, a progressive reversible switch adapted to controleach of said units, means ac tuating one of said switches in accordance with the tension of said sheet,‘ and manual means to actuate the other of said‘switches. 25 variations in tension of said sheet due to varia limits of its movement. tion of said valve,'means responsive to variations 10 in tension of the sheet due to variations in mois ture content thereof to actuate one of said units, and a second control means adapted to actuate the other of said units. ' 25 9. A temperature-control device for paper mill drying rolls over which a sheet of paper is passed to be dried comprising, in combination, a source of heat supply to said rolls, a valve adapted to control said supply, a pair of reversible motor 30 control units adapted to jointly control the posi tion or said valve, a progressive reversible switch adapted to control eachof said units, means ac tuating one of said switches in accordance with the tension'of said sheet, and thermostatic means responsive to the roll temperature adapted to ac~ tuate the other of said. switches. 10. A temperature control device for paper mill drying rolls over which a sheet of paper is passed to be dried, comprising, in combination, a source 40 of heat supply to said rolls, a, valve adapted to control said supply, a lever adapted to control said valve, amember‘ adapted to press against said sheet for tensioning the same, integrating means responsive to the average position of said 45 member over given time intervals, a belt actu ated by said integrating means to control said lever between limits, and a motor-control unit adapted to control said lever within said limits, said motor-control unit also being actuated by 50 said integrating device. ' . ‘ 11. A temperature control device for paper mill drying ‘rolls over which a sheet of paper is passed to be dried, comprising, in combination, a source of heat supply to said rolls, a valve adapted to 55. controlsaid supply, a lever adapted to control said valve, 9. member adapted to press against said sheet m tensioning thesame, integrating means responsive to theaverage position of said member over given time intervals, a belt actuated by said integrating means to control said lever between limits, a motor-control unit adapted to control said lever within said limits, said motor» control unit also being actuated by said inte grating device, and a master control adapted'to change the range of control of said motor-con trol unit. 12; In a paper mill, in combination, a drying roll adapted to receive a sheet ofv paper to be dried, a source of steam supply therefor, a con trol valve for said steam supply, a pair of motor control units adapted to independently control said valve, means automatically operating one of said units in response to variations in the mois ture ‘content of said sheet, and a second control 76 means actuating the other of said units. 6 2,185,627 ' 13. A device for controlling the temperature of drying rolls over which a sheet of paper is passed passed to be dried, whichcomprises a source of heat for said rolls, a proéressive reversible con to be dried, which comprises a member adapted to press against the sheet for tensioning the same, a ?uid cylinder, means responsive to movement of said member to control the supply of ?uid to said cylindena piston actuated by said ?uid, a source of heat for said rolls, and means actuated in accordance with the position of said piston to 10 control said source for varying the temperature trol means for controlling said source, means of said rolls so as to compensate for variations in adjustment of said control means with respect to said belt. moisture of the incoming sheet. 14. A device for controlling the temperature of drying rolls over which a sheet of paper is responsive to variations in the moisture content of the sheet, a belt actuated by said last means, said belt passing over said control means for actuating the same, means to limit the movement of said control means, said belt being adapted to slide thereover when the limit of movement 01’ said control means has been reached or to permit 10 ' RAZOR J. SMITH.