US2122362A - Control mechanism for paper making machines - Google Patents

Description

June 28, 1938. A STANTON 2,122,362

CONTROL MECHANISM FOR PAPER MAKING MACHINES Filed April 30, 1935 I mue/zfors Patented June 28, 1 938 CONTROL MECHANISM FOR PAPER MAKING MACHINES Avery H. Stanton, Dedham, Mass, assignor to Eldon Macleod, Frank A. Morrison, Cameron Maeleod, Leslie Soule, and Sullivan A. Sargent, Jr., trustees, doing business as Mason-Neilan Regulator Company, Boston, Mass.

Application April 30, 1935, Serial No. 18,979

7 Claims. (Cl. 34-48 This invention relates to moisture control mechanism for paper making machines, wherein the paper is passed around steam heated drying cylinders, and relates more particularly to apparatus for automatically controlling the supply of steam to the cylinders, whereby their temperature and consequently the moisture content of the paper is regulated. It is, of course, of great importance in paper making that the moisture content of the paper be closely regulated to maintain a small but uniform moisture content as the paper is delivered from the machine. Heretofore the many variable factors aiiecting moisture control have prevented the close regulation desired. For instance the factors which may afiect the moisture content of the paper are .changes in weight of the paper sheet, change in density and freeness of stock, change in air humidity, change in the machine speed, as well as change in temperature of the drying cylinders due to previous change in pressure or rate of flow of the steam supplied to the cylinders or to change in the rate of condensate removal from the drying cylinders. It is also important in moisture control that the control mechanism be instantly responsive to' changes in conditions, for if there is time lag inresetting the temperature control point in the dryers, the mechanism may be re-setting for conditions which no longer exist a few minutes later. Similarly it is important that the mechanism does not over-control or go too far in each direction, as this produces hunting.or undesirable fluctuation in the range of moisture content.

My invention comprises briefly the utilization of two instruments, one a tension roll responsive to changes in tension of the paper sheet due to moisture content, and the other a temperature bulb responsive to changes in temperature in the drying cylinder, which instruments operate the control valve governing the supply of steam to thecylinders through their separate or joint action. An independent pressure system, preferably air and ordinarily exhausting to the atmosphere is used as an operating pressure to actuate the control valve governing the steam supply, and operates through a pilot mechanism and exhaust valve, comprising an exhaust orifice and flapper lever. Compensation to prevent over-control or "hunting is provided from the operating air pressure, which operates to check or compensate the action of the exhaust valve in one direction in response to changes in moisture content or temperature of the cylinders by providing a slight movement of the exhaust valve in the opposite direction. It is to be understood that instead of joint tension roll and temperature control, the joint control may be taken from tension roll and the pressure of the heating medium, or from tension roll and from rate of flow of the heating medium, across any form of orifice, both pressure and flow connections being taken from the downstream side of the valve. It is also to be understood that moisture control may be effected in any suitable manner, tension roll control merely being one of several suitable methods.

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation, and it is not intended to limit the invention claimed herein beyond the requirements of the prior art.

In the drawing:

Fig. 1 is a diagrammatic view of my control mechanism in a paper making machine.

In the drawing, Ill represents a mechanism for maintaining an adequate and constant pressure of air or other suitable fluid for operating the independent pressure system, and as this device forms no part of the invention claimed it need not be described in detail. The operating air pressure is supplied through pipe H and is suitably filtered through the filter Hill, the pressure gauge l5 indicating the operating pressure. The air passes through pipe II to a pilot valve mechanism 20. The branch pipe I! having a restricted orifice I8 by-passes the stream of air and ordinarily exhausts it to the atmosphere through exhaust orifice is at the lower end of branch pipe H. A flapper lever 55, as actuated by the three responsive instruments to be later described constitutes an adjustable mounting 80 which oper-j ates to close the exhaust orifice l9 and thereby build up pressure in branch pipe I! below the restricted orifice l8.

Branch pipe I1 connects with the pilot valve mechanism 20 through the pipe 2| below the restricted orifice l8 which leads into a central diaphragm chamber 22. A stem 24 abutting the top side of the diaphragm chamber 22 forms a valve between pipe II and chamber 25. A similar stem 26 abutting the bottom side of the diaphragm chamber 22 forms an exhaust valve between the chamber 21 and the atmosphere. Both chambers are connected on the outside by pipe 28 ing the amount of opening of valve 30, whichiis calibrated within definite pressure limits. Pipe 32 connects the operating pressure in pipe 29 to I the Bourdon tube 65 of the adjustable mounting 80 for'providing compensation, as later described. Control valve 30, which is preferably a diaphragm motor valve, controls the admission of steam to the drying cylinders 36, and is shown for purposes I of illustration as normally closed, opening on applied air pressure to diaphragm 36a.

The drying cylinders 36 may be one or more, but are here shown as a battery of three with one at the top and two arranged below on either side on asuitable frame 34.

Steam is supplied to the drying cylinders 36- through pipe 35, having connections 3511 leading to each cylinder 36. It is understood that the sheet of paper 33 passes around the rotating drying cylinders 36, and that any form of heating medium, as hot water, hot air, in addition to steam may be used.

Onthe closing of exhaust orifice l9, pressure in diaphragm chamber 22 builds up, forcing valve 26 closed and valve 24 open allowing pressure from pipe II to enter directly into chamber 25, flow through connecting pipe 28 into chamber 21 and equalize the pressures therein. When pressure in chambers 25 and 21 balances the force in central chamber 22, the valve 24 closes to prevent pressure in chamber 25 from increasing. Air pressure in pipes 28 and 29, in a closed chamber, immediately reacts on diaphragm 30a. to par tially open control valve 30, permitting more steam to flow into the drying cylinders 36. .t the same time air pressure reacts through pipe 32 on the Bourdon tube segment 85 to provide compensation, as later described.

A thermostat 31 or other temperature responsive instrument containing an expansible fluid is provided in one of the drying cylinders 36 preferably in a dryer subsequent to the tension roll location, and preferably located inside the dryer from the front" end or in the steam inlet to the dryer. In the drawing, however, for cenvenience of illustration, the connection is shown at the steam inlet to the dryer. The thermostat 31 connects through tubing 38 to coil 39 rigidly fixed at one end and at its free end connected to arm 40 which in turn transmits motion to flapper lever 56. The coil 39 may be helical, spiral or a segment of a Bourdon tube or other device responsive to pressure (i. e. pressure responsive thermostat 31 contains expansible fllLid).

A tension roll device 60, of suitable construetion, as known in the art, is mounted adjacent one of the cylinders 36, to bear yieldingly against the travelling sheetef paper. As is well known the tension roll device may comprise a roller 6|, a bell crank lever 62 pivotally supported at point 63 to the frame 34, and a lever 64 also pivotally supported at 63 and'movable as a unit with lever 62 and having the counterweight 65 attached to one end. By this device the roller 6| is yieldingly held against the face of the paper sheet 33 betweentwo of the cylinders 36, where the paper is subject to slight sag when its moisture content exceeds a predetermined amount and tends to straighten when the moisture content is reduced below that amount. This alternate sagging and stiffening or straightening of the paper sheet in response to its moisture content is used for controlling the moisture content in the pap A gauge 3| connected to the pipe 29 indiby regulating the amount of steam supplied to the drying cylinders. 'The degree of sheet moisture content can be varied as desired by changing counterweight 65. Movement of tension roll lever 64 compresses or allows to expand a bellows 1| provided in a closed hydraulic pressure system 10 comprising the bellows 1|, tubing 12, a second bellows 13, spring resisted, and connected to a Bourdon tube 14, pictured as a segment rigidly mounted at one end and at its free end connected to an extension 56a. of flapper lever 56. Bellows 13 is utilized to provide correct deflection of Bourdon tube 1.4 by absorbing a portion of the pressure created by change in position of bellows El.

It will be seen, therefore, that my moisture control mechanism controls from the separate or joint action of two instruments, the tension roll 66 being responsive to changes in tension of the paper sheet, and the thermostat 31 responsive to temperature changes in' one of the drying cylinders 36. through their separate or joint action to control the supply of steam. to the cylinders through control valve 30, which is set in operation by regulating the amount of exhaust to the atmosphere of the independent air pressure system through movement of flapper lever 56,

In case the paper sheet breaks, I have provided a shut-off device for the operating air pressure system comp-rising valve 90. As the paper sheet breaks the tension roll lever 64 drops and operates to close the valve 90. This in turn shuts off the air pressure operating control valve 30 and allows it to close, thereby shutting oh the steam supply to the cylinders.

The operation of my device is as follows:

As the-temperature in the cylinder 36 carrying the thermostat 31 rises, the expansive fluid in the thermostat 31 increases its pressure and unwinds the Bourdon tube 39 which acting through arm 40 lowers flapper lever 56.partially opening exhaust orifice l9. Air pressure in pipe I 1 below the restriction l6 then decreases in diaphragm chamber 22 to release the pressure from chamber 21 and pipe 29 through valve 26 from the diaphragm 30a of motor valve 36, to partially close valve 30. This decreases the flow of steam through pipe 35 and branch pipes 35a and further increase in temperature in cylinders 36 is prevented. On a decrease in temperature in cylinder 36 carrying the thermostat 31, the action is the opposite. Likewise if the paper sheet be- .comes excessively dry, because of any one of the variable factors which affect its moisture content, the paper sheet passing between two of the cylinders will tend to straighten, and this increase of the paper sheet tension will cause the tension roll 60 to yield slightly, thereby elevating lever 64 and compressing bellows 1| in the closed hydraulic pressure system 16, and increasing the pressure therein which unwinds Bourdon tube 14, thereby moving flapper lever 56 away as to partially open orifice l9. Again the independentair pressure system operates in the same manner as with the increase of temperature of thermostat 31, and allows control valve 30 to partially close, thereby diminishing the amount of steam supplied to the cylinders 36. Likewise on an increase in moisture content in the paper sheet,

time before a change in temperature in the cyl- These two instruments operate inders or the moisture content in the paper can be reflected through thermostat 31 or tension roll to re-set the motor valve 30, I have provided compensation through the operating pressure, which works in an opposite direction to the thermostat 31 or tension roll 60, and whose action is immediately effective on the setting of flapper lever 56. The setting of flapper 56 as actuated by changes in temperature of the cylinders 36 and changes in tension in the paper sheet is immediately compensated or counteracted by the operating pressure without waiting for the impulse to go through the thermostat 81 or tension roll 60. For instance as temperature in cylinder 36 rises and flapper 56 moves downward through the action of the helical coil 39 to partially open exhaust orifice l9 and the operating pressure decreases to partially close control valve 30, the decrease in the operating pressure is immediately reflected in the Bourdon tube segment 85, which tends to wind and raise flapper 56, thus partially closing exhaust orifice l9. On a decrease in temperature in cylinder 36 the action of Bourdon tube 85 is opposite. Likewise changes in the position of flapper lever 56 induced by changes in the tension of the paper sheet reflected through the tension roll 60 are likewise opposed by the action of Bourdon tube 85 acting in opposite direction thereto.

It is to be observed that the effect from the operation of the Bourdon tube 85 is to decrease the effect from either tension roll 60 or thermostat 31 in repositioning the control valve. The effect from tension roll 60 less the effect from Bourdon tube 85 having been positive and causing a reposition of control valve 30 then an opposing action comes from thermostat 31 due to the variation in temperature caused by the reposition of valve 30 and the effect from 31' is to compensate further thus preventing any hunting or overtravel. It further should be observed that the reactions of thermostat 3! occur as fast as the changes within the dryer. The degree of effectiveness is from 85 and 31 and is proportional to the ratio of fulcrum arms 40, 56 and 56a as set for the particular installation which is adjustable. Thus the compensating action from the operating pressure stabilizes the control instrument and prevents the usual wide fluctuation, thereby rendering this type of control extremely accurate.

By means of my device I am able to, obtain moisture control of the paper sheet within closer limits than before possible with tension roll control and by eliminating hunting and overcontrol a uniform steam flow to the dryers is obtained, thus providing uniform heat input to the sheet under uniform conditions of basis of weight and effective drying. This uniform flow I further aids in boiler plant operation. Because of the control from thermostat 31 an anticipatory action is provided wherein changes in steam pressure afiecting the temperature of the dryers will re-set the valve before such changes can alter the moisture content of the sheet. Thus a large amount of manual control to meet varying conditions affecting moisture content of the paper is eliminated.

I claim:

1. A moisture control mechanism for paper making machines comprising a drying cylinder, the temperature of which is to be controlled, a source of steam supply for heating said cylinder, a control valve governing supply of steam to said cylinder, a pilot mechanism utilizing an independent source of pressure for operating said control valve and ordinarily exhausting to the atmosphere, an exhaust valve governing the exhaust from said pilot mechanism, an instrument actuated by varying tension of the paper, another instrument responsive to a variable characteristic of said drying cylinder, joint means oper-- trol valve and ordinarily exhausting to the atmosphere, an exhaust valve governing the exhaust from said pilot mechanism, means for di- Verting. said pressure to operate said control valve on the closing of said exhaust valve, an instrument actuated by varying tension of the paper, another instrument responsive to the temperature of said drying cylinder, joint means operated by the action of said instruments for actuating said exhaust valve, and means responsive to the operating pressure afforded by said pilot mechanism for counteracting movement of said exhaust valve.

3. A moisture control system for paper making machines, comprising a drying cylinder, the temperature of which is to be controlled, a source of steam supply for heating said cylinder, a control valve governing the supply of steam to said cylinder, a pilot mechanism utilizing an independent source of pressure for operating said control valve and ordinarily exhausting to the atmosphere, an exhaust valve governing the exhaust from said mechanism, a movable flapper controlling said exhaust valve, a lever supporting said flapper at one end, a second lever supporting said flapper at its other end, an instrument responsive to the temperature of the drying cylinder, a coil actuated by the temperature responsive instrument for moving the flrst flapper supporting lever, an instrument actuated by the varying tension of the paper, a coil actuated by said second instrument for moving said second flapper supporting lever, and so actuating said exhaust valve through the action of said coils, a third coil responsive to the operating pressure afforded by said pilot mechanism for counteracting the movement of said exhaust valve as actuated by the flrst two coils;

4. A- moisture control mechanism for paper making machines comprising a drying cylinder, the temperature of which is to be controlled, a source of steam supply for heating said cylinder,

a control valve governing supply of steam to valves to divert said pressure to the control valve for operating the same on the closing of said exhaust valve, an instrument actuated by varying tension of the paper, anotherinstrument responsive to a variable characteristic of said drying cylinder, and joint means operated by the action of said, instruments for actuating said exhaust valve.

5. A moisture control mechanism for paper making machines comprising a drying cylinder,

the temperature of which is to be controlled, a

source of steam supply for heating said cylinder, a control valve governing supply of steam to said cylinder, a pilot mechanism utilizing an independent source of pressure for operating said control valve and ordinarily exhausting to the atmosphere, an exhaust valve governing the exhaust from said pilot mechanism, said pilot mechanism including a casing, a pair of diaphragms dividing said casing into-"two outer chambers and an inner chamber, a supply valve and a waste valve in said outer chainbers governing the supply and waste of pressure by which said control valve is operated; the pressure from said independent source expanding said inner chamber and actuating said supply and waste valves to divert said pressure to the control valve for operating the same on the closing of said exhaust valve, an instrument actuated by varying tension of the paper, another instrument responsive to a variable characteristic of said drying cylinder, joint means operated by the action of said instruments for actuating said exhaust valve, and

- means responsive to the control valve operating pressure afforded by said supply and waste valves ,t for counteracting movement of said exhaust valve. 6. A moisture control mechanism for paper making machinescomprising a drying cylinder, the moisture in the paper sheet passing over which is to be controlled, a source of heating medium for heating said cylinder, a control valvegoverning supply of heating medium to said cylinder, a pilot mechanism utilizing an independent source of pressure for operating said control valve, an element responsive to the temperature of said drying cylinder, and joint means operated by the tension of said sheet and by said temperature responsive element-for controlling said pilot to reset the temperature of said cylinder in proportion to changes in sheet moisture.

7. A moisture control mechanism for paper making machines comprising a drying cylinder, the moisture in the paper sheet passing over which is to be controlled, a source of heating medium for heating said cylinder, a control valve governing supply of heating medium to said cylinder, a pilot mechanism utilizing an independent source of pressure for operating said control valve, an element responsive to temperature of said drying cylinder, an element responsive to the operating pressure afforded by said pilot for partially ofisetting a change in said pressure, and means operated jointly 'by the tension in said sheet, by said temperature responsive element and by said pressure responsive element to reset the temperature in said cylinder substantially in proportion to changes in sheet moisture.

AVERY H. STANTON.

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