US2120079A - Automatic steam control for paper machines - Google Patents

Description

June 7, 1938. F. A. STICKLE 2,120,079

AUTOMATIC STEAM CONTROL FOR PAPER MACHINES Filed Oct. 2, 1936 :z 29 I; 22 40 26 70 Z 35 a/ 7 5- Z/ 37 6 INVENTOR.

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0 ATTORNEYS I Patented June 7, 1938 UNITED STATES AUTOLIATIC STEAM CONTROL FOR PAPER MACHINES Fredrick A. Stickle, Indianapolis, Ind., assignor to Stickle Steam Specialties Company, Indianapolis, Ind., a corporation Application October 2,

3 Claims.

This invention relates to an automatic steam control for paper machines. q

In the manufacture of paper, a continuous web of paper is dried by passing it about a series of rotating drying rolls heated by steam admitted to the interior of the rolls. The water content of the incoming paper is subject to variation from time to time, making it necessary to vary the pressure and temperature of the steam supplied to the rolls to secure a uniformly dried finished product. When the web of. paper is not thoroughly dried in the process, it becomes slack on the rolls, and when over-dried, it becomes excessively tight and may even break. hi variation in tension is utilized to automatically control the steam supply. The steam control is accomplished by means of a tension roll engaging the web of paper in a position to be moved in one direction when the web tightens and in the other direction when the web slackens. The movement of the roll is transmitted through suitable mechanism to the steam throttle valve controlling the steam supply to the drier in such manner as to admit more steam when the paper is too wet and less when too. dry. The tension roll must necessarily be at a point where the paper has reached a sufficiently dry state to withstand the pressure of the tension roll upon the web and this point must be somewhat remote from the, receiving end of the machine. For that reason, a change in the water content of the incoming paper will not be reflected immediately in a change in tension of the web at the tension roll. There is, thus, a time lag between cause and effect which results in a certain amount of over-control if changes in moisture content of the paper are abnormally sudden or temporary. With this prior art control, when the web breaks, for any reason, the pressure roll is free to move to an extreme position, which results in fully opening the steam valve. Since it is not desirable to overheat the rolls during the shut down resulting from a break in the web, it is necessary toclose the valve by hand as soon 5 as such a break occurs.

1936, Serial No. 103,708

supply which might be caused by sudden or temporary changes in the moisture content of the paper. In case of a break in the web, the tension control ceases to function and the superimposed auxiliary control operates to maintain the steam pressure in the drier between predetermined maximum and minimum limits. These limits are so chosen that the rolls are neither overheated nor permitted to cool unduly and are, therefore, immediately ready for a resumption of operation when the web has again been fed through the machine.

Other objects and features of the invention will be understood from the accompanying drawing and the following description and claims:

Fig. 1 is an elevational view of a portion of a paper machine having the invention applied thereto. This figure is substantially diagrammatic, the frame of the machine and other supporting parts being omitted to disclose the invention more clearly; Fig. 2 is an enlarged elevational view with parts in section of a portion of Fig. 1. Fig. 3 is a sectional view taken on the line 33 of Fig. 2.

In the drawing. there is shown, by way of illustration, a preferred form of the invention. Three drying rolls III of a multiple roll paper machine are shown. A web ll of the paper being dried is trained about the rolls in the usual manner. The drying rolls are supplied with steam by means of a steam main l2 and supply pipes l3. Condensate is removed from the rolls by means of condensate pipes l4 and a return main IS. The escape of condensate is regulated by oriiice valves 16 of the usual form placed in the condensate lines M. The pressure of steam within the rolls, and therefore, the temperature of the rolls, is controlled by a throttle valve II in the steam main l2. Valves l8 are provided in the steam pipes I3 and return pipes 14 to cut out the operation of an individual roll when desirable.

A tension roller l9 engages the web of paper between two of the drying rolls Ill. The tension roll is mounted on a shaft 20 in turn .mounted in a fitting 2i secured to the end of a lever arm 22. The lever arm 22 is fixed to a stub shaft 23 rotatably mounted on a suitably supported stationary frame 24. The stub shaft 23 has fixed thereto a bushing or collar 25 to which there is secured, by means of bolts 26, the hub 21 of a lever arm 28. The bolts 26 operate in slotted openings 29 in the hub 21 and may thus be used to adjust the angular relationship between the lever arm 28 and the tension roll IS. The lever arm 28 is provided at its outer end with a suitable opening through which extends the valve stem 30 of a pilot valve 3|. Said stem has threadedly engaged therewith a pair of seats 32 engaging the end of the lever arm and a pair of lock nuts 33 retaining said seats in proper position. The valve 3| is secured to the frame 24 and the valve stem 30 is slidably guided at its upper end in a bushing 34 secured to said frame.

The hub 21 has secured thereto by means of clamps 35, a lever arm 36on the outer end of which there are hung counterweights 31 by means of which the pressure of the tension roll l9 on the web of paper may be adjusted.

The valve 3| is connected to a suitable source of water or other motive fluid under pressure by a pipe 38 in which there is placed a common form of pressure regulator 39 which insures a uniform fluid pressure at the valve 3|. The discharge side of the valve 3| is connected by a pipe 40 to. the lower end of a cylinder 4| in which there is operating a piston 42. A leakoff valve 43 is also connected to the pipe 46 and is adjusted to permit the fluid passed by valve 3| to escape at a predetermined rate, depending upon the pressure in the pipe 40 and cylinder 4|. The piston 42 is connected to a piston rod 44, on the upper end of which there are carried a number of weights 45; A chain 46 is connected by a hook 41 to the upper end of the piston rod 44. The chain 46 passes over a pulley 48 suitably supported on an overhead support 49 and is connected at its opposite end to a lever 59 serving to open and close the valve IT. The lever 50 carries a counterweight 5| which insures the closing of the valve when the chain 46 is slackened by an increase of pressure in the cylinder 4|.

In the operation of the apparatusso far described, the parts are adjusted to assume a normal position when the web of paper in the tension roll has the proper tension. In this normal position, the valve I1 is opened the proper amount to maintain a steam temperature in the drying rolls which will maintain the web in the desired state of dryness so long as the moisture content of the incoming paper remains unchanged. If the water content increases, the web slackens and the weights 31 operate to draw the lever 36 and the lever 28 downwardly, thus partially closing the' valve 3|; The movement of this valve decreases the supply of water to the cylinder 4| The water, therefore, escapes through the valve 43 at a more rapid rate than it is supplied and permits the piston 42 to move downwardly under the action of the weights 45. The downward movement of the piston is transmitted through the chain 46 to the lever 5| which is lifted to partially open the valve l1 and to admit more steam to the drying rolls. 'The increase in steam pressure thus caused results in an increase in temperature which serves to dry the paper at a more rapid rate and to restore the normal condition of the web.

Similarly, if the water content of the incoming paper decreases, the web, before reaching the roller l9, becomes more thoroughly dry. It, therefore, tightens and forces the roller l9 to the left in Figs. 1 and 2. This movement elevates the lever 28, opens the valve 3| and causes a building up of pressure in the pipe 40 and :tially close the valve Thus, a lower pressure and temperature is produced in the drying rolls and this change tends again to restore the normal condition of the web.

In order to modulate the action of the tension control just described, to prevent over-control and to prevent full opening of the valve if the Web breaks, there is provided an auxiliary control which operates in response to the physical condition of the steam supplied to the drying rolls. In the example shown herein, this auxiliary control operates in response to the temperature of such steam, but it may be operated equally well in response to pressure since there is a definite relation between the temperature and pressure of the unsaturated steam used for drying. In the example shown herein, there is provided a sampling pipe ortube 52 supplied with steam from the main l2 by a pipe 53. The pipe 52 is drained of condensate by a pipe 54 supplied with an orifice valve 55'similar to that used for the drying rolls. The steam in the pipe 52 is thus maintained at the same temperature and pressure as the steam in the drying rolls. Suitable pressure gauges 56 and 51 are supplied to indicate the supply pressure and drainage pressure respectively and a thermometer 58 is supplied to indicate the temperature of the steam in the sampling pipe. A test cook 80 connected to the orifice valve 55 is opened periodically to determine whether or not the sampler is being properly drained.

A thermostat bulb 59 is inserted in the pipe 52 and is connected by a flexible tube 60 to the interior of a thermostat bellows 6| carried upon a frame 62 secured to the frame 24. The bulb 59 and tube 68 are supplied with the usual volatile fluid which expands upon heating and causesa corresponding expansion of the bellows 6|. A seat 63 forms the upper part of the bellows chamber 6| and has secured thereto a vertical stem 64 slidably guided in a threaded tube 65 secured to the frame 62. A compression spring 66 abuts against the cap 63 and against a cup 61 which is retained in an adjusted position by an adjusting screw 68 threadedly engaging the tube 65. At its upper end, the stem 64 has secured thereto a collar 69 in which there is slidably retained a second stem III which may be clamped in place by a thumb screw The stem III is slidably guided in suitable bushings mounted upon the frame 24 and carries spring abutments l2 threadedly engaged therewith.

the thumb screw H is tightened. Thereafter,

a change in-the condition of the web results in a corresponding change in the pressure and temperature of the steam supplied to the drying rolls as before, but the change is opposed and modulated by the movement of the stem 10 and its associated springs 13 under the influence of the change in temperature in the sampler 52. For example, a slackening of the web calling for increased temperature results first in the opening of the valve II to supply steam at this temperature. This in turn results in an increase of temperature at the thermostat bulb 59. The

expansion of the volatile fluid in said bulb pushes the stems 64 and I upwardly and exerts an upward pressure on the lever 28 through the springs I3, thus opposing the movement of said lever due to the slackening of the web. The springs I3 and 66 are so adjusted that the opposing force prevents over-controlling on abnormally sudden and temporary changes but does not prevent suiiicient movement of the lever 28 to correct for normal changes in the water content. If an extreme change in the water content of the paper occurs, the adjustment of the thermostatic control is such that it prevents a corresponding extreme change in the temperature of the steam supplied. Such abnormal changes in the condition of the web are usually of short duration and, if permitted to influence the steam control unhindered, would result in excessive changes in the steam pres sure.

If for any reason, the web ll breaks, the springs 13 act on the lever 28 under thermostatic control to prevent the full opening of the valve I! which would normally result from the downward movement of said lever. The control operates to maintain the steam pressure and temperature in the drying rolls within predetermined limits until normal conditions can be restored.

The foregoing specification describes a preferred form of the invention, the details of which may be varied by those skilled in the art without departing from the scope thereof as defined by the appended claims. For example, the auxiliary control may be accomplished in response to pressure changes in the steam supply as well as temperature changes. Since there is a definite fixed relation between the temperature and pressure of steam, such a pressure control is considered the mechanical equivalent of the temperature control herein described.

In another variation, the thermostat bulb 59 may be placed within one of the drying rolls instead of in the sampler as shown herein. However, it is often necessary to take one or more of the drying rolls out of operation by shutting ofi its steam supply. The use of one of these rolls as a sampler makes it impossible to cut out the operation of that particular roll without destroying the operation of'temperature control. For that reason, I much prefer to use the sampler.

The invention claimed is:

1. Control apparatus for paper machines having drying rolls including a steam line supplying steam to the drying rolls, a valve in said line controlling the flow of steam therein, a tension roll engaging a web of paper passing through said machine and tending to be moved in one direction when said web slackens and in the other direction when said web tightens, a movable member operatively connected to said tension roll and movable thereby, means operatively connecting said movable member and said valve and tending to close said valve when said member is moved in response to a tightening of the web and to open the same when said member is moved in response to a slack ening of the web, and a thermostat responsive to the temperature of the steam supplied to said drying rolls and operative connections between said thermostat and said movable member tending to move said movable member in the direction to close said valve when the temperature of said steam increases and to open said valve when said temperature decreases.

2. Control apparatus for paper machines having drying rolls including a steam line supplying steam to the drying rolls, a valve in said line controlling the fiow of steam therein, a tension roll engaging a web of paper passing through said machine and tending to be moved in one direction when said web slackens and in the other direction when said web tightens, a movable member operatively connected to said tension roll and movable thereby, means operatively connecting said movable member and said valve and tending to close said valve when said member is moved in response to a tightening of the web and to open the same when said member is moved in response to a slackening of the web, an expansible element, means responsive to the condition of the steam supplied to said drying rolls and tending to expand said element when the temperature of said steam increases and to contract the same when said temperature decreases, a stem movable by expansion and contraction of said element, and opposed compression springs interposed between said stem and said movable member and tending to move the same in the direction to close said valve when said expansible member is expanded and to close the same when said member is con tracted.

3. Control apparatus for paper machines having drying rolls including a steam line supplying steam to the drying rolls, a valve in said line controlling the fiow of steam therein, a tension roll engaging a web of paper passing through said machine and tending to be moved in one direction when said web slackens and in the other direction when said web tightens, a movable member operatively connected to said tension roll and movable thereby, means operatively connecting said movable member and said valve and tending to close said valve when said member is moved in response to a tightening of the web and to open the same when said member is moved in response to a slackening of the web, an expansible element, means responsive to the condition of the steam supplied to said drying rolls and tending to expand said element when the temperature of said steam increases and to contract the same when said temperature decreases, a stem longitudinally movable by expansion and contraction of said element, said stem being manually adjustable as to length, and opposed compression springs interposed between said stem and said movable member and tending to move the same in the direction to close said valve when said expansible member is expanded and to close the same when said member is contracted.

FREDRICK A. S'ITCKLE. 65

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