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Publication numberUS2852860 A
Publication typeGrant
Publication date23 Sep 1958
Filing date18 May 1955
Priority date18 May 1955
Publication numberUS 2852860 A, US 2852860A, US-A-2852860, US2852860 A, US2852860A
InventorsFrederick A Stickle
Original AssigneeStickle Steam Specialties Comp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Automatic steam control for paper machines
US 2852860 A
Abstract  available in
Images(4)
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Claims  available in
Description  (OCR text may contain errors)

P 23, 1958 F. A. STICKLE 2,852,860

AUTOMATIC STEAM CONTROL FOR PAPER MACHINES Filed May 18, 1955 4 Sheets-Sheet 1 M m 25 1 A Izo /J z! 25 72 51% LL V Z 2' e 40. L; W 32 54 I; INVEN TOR.

FRA'D'R/CK /9. 517cm. 5.

AUTOMATIC STEAM CONTROL FOR PAPER MACHINES Filed May 18, 1955 F. A. STICKLE Sept. 23, 1958 4 Sheets-Sheet 2 INVENTOR. REDER/CK /7. 577 was. 2

2,852,860 AUTOMATIC STEAM CONTROL FOR PAPER MACHINES Filed May 18, 1955 F. A. STICKLE Sept. 23, 1958 4 Sheets-Sheet 5 w\\\ a (w L Q R. K H m m N R Q m M m m n m y FF 3 r M \M O O 3 R N I fi O/w NR R B 2 QM n wvM vs 2,852,860 Patented Sept. 23, 1958 AUTOMATMI STEAM CONTROL FOR PAPER lVIAHINES Frederick A. Stickle, Indianapolis, Ind., assignor to Stickle Steam Specialties Company, Indianapolis, Ind., a corporation Application May 18, 1955, Serial No. 509,374

12 Claims. (Cl. 34-49) This invention relates to an automatic steam control for the drying rolls of paper machines and including a remote control and recorder therefor, reference being had to my Letters Patent No. 2,120,079, patented June 7, 1938, and entitled Automatic Steam Control for Paper Machines.

This invention generally relates to the control of steam admitted to the interior of paper drying rolls for effecting the drying of paper passing thereover, and wherein the moisture content of the incoming paper is subject to variation from time to time, making it necessary to vary the pressure and temperatures of the steam supplied to the rolls for securing uniformity in the drying of the finished product. For this purpose a tension roll is mounted for engagement with the paper as it passes between the drying rolls much in the manner set forth and described in the foregoing patent.

Through variations in the moisture content of the paper the paper at the point of contact with the tension roll tends to become more taut, moving the roll in one direction when dry, and looser permitting the tension roll to move in the opposite direction when wet. Such movement of the tension roll by the Web of paper according to its moisture content functions to effect the degree of opening or closing of the master steam valve controlling the steam admitted to the interior of the rolls.

Broadly speaking, it is the purpose of this invention to provide a pneumatic control of the master steam valve by the tension roll coupled with remote manual or automatic adjustments therefor including maintenance of a permanent record by way of a graph indicating the steam pressure and moisture content of the paper during predetermined periods of time and any fluctuation thereof. Thus, the control of this invention automatically regulates the steam pressure in the drying rolls to increase or decrease the drying rate in accordance with the moisture content of the sheet passing over the dryers regardless of variation thereof, machine speed or the weight of the paper.

By reason of the automatic tension and pressure control a faster steam flow is permitted without violent fluctuation; more sensitive and convenient adjustments are provided; and a 24 hour chart is recorded to provide a permanent record of steam pressure in the dryers, moisture variation in the sheet as well as time and duration of wet end breaks. Thus by indicating the moisture variations in the sheet as it passes over the dryers the control of this invention provides information formerly obtained only by expensive and complicated equipment.

The tension phase of the control operates from variation in moisture content of the sheet as indicated by the draw on the sheet as it passes over the dryers, the slightest change in the draw actuating a floating tension roll connecting with a sensitive pilot valve. The pilot Valve controls the master steam valve to increase or decrease steam flow to the dryers through a pneumatic pressure system.

The invention further contemplates a control embodying a tension roll assembly, a diaphragm motor valve and a remote controlling and recording instrument panel, the tension roll assembly pneumatically actuating the diaphragm motor valve which in turn controls the master steam valve. The pneumatic actuation of the motor Valve is effected through controls on the instrument panel which permits not only remote control of the system, but provides both visual and permanently recorded observations thereof.

One feature of the invention resides in the structure of the tension roll adjustment and the accurate balancthrough wide variations in the opening and closing of the master steam valve.

A further feature of the. invention resides in a cam actuated pilot valve for controlling the air pressure in the pneumatic controlsystem, which pilot valve is cam actu-,

ated by movement of the tension roll for controlling the air pressure to the master steam valve control and the air motor control for automatically varying the tension on the tension roll.

A further feature of the invention resides in. the remote control panel for indicating the steam pressure and temperature to the drying rolls and permitting pneumatic control thereof, said remote control additionally including a permanent record of the steam pressure in the drying rolls and moisture variation in the sheettogether with a recording of any time and duration of wet end breaks in the paper.

A further feature of the invention resides in the pneumatic actuation of the control in event of a Wet end break in the paper web such as to remotely indicate. such break, record the time and duration thereof and additionally maintain the temperature and pressure of the steam in the drying rolls during the period of the break so that the drying may be renewed under the same conditions upon the drying action being resumed.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a perspective view of the tension roll assembly.

Fig. 2 is a shematic illustration of the pneumatic controls in association with the tension roll assembly as shown in Fig. l. i

Fig. 3 is a side elevation of the tension roll assembly with portions shown in section.

Fig. 4 is an enlarged sectional view of a portion of the pilot valve shown in Fig. 3, with parts broken away and removed.

Fig. 5 is a schematic illustration of the 4-way routing valve shown in Fig. 2 in dilferent positions as indicated at A, B, C and D. r

Fig. 6 is a schematic illustration of the 3-way routing valve shown in Fig. 2, illustrating its effective positions A and B.

Fig. 7 is a layout of the permanent recording 24 hour chart showing steam pressure and moisture content together with wet breaks in the paper during the drying operation.

Fig. 8 is a schematic illustration showing the relation of the tension roll to the paper drying rolls and the wet break signalling device.

In the drawings, reference being made to Fig. 8, there is indicated a group of paper drying rolls 10, 11 and 12 over which a web ofpa'per '13 is' caused to pass for removing the moisture content therefrom duringthe drying'operation of a paper "making machine. Positioned for engagement with the paper web, and under suitable tension there is provided a tension roll 14. Steam is introduced into the drying rolls 10, 11 and 12 in the usual Well known manner from the steam pipe 15 connected with a source of steam passing into the pipe 15 and controlled by a master steam valve 16. The master steam valve 16 is controlled in the usual manner by a diaphragm motor valve 17 actuated by air pressure delivered thereto by the air line 18, and includingaspring adjusting block 19. Thus according to the pneumatic actuation of the diaphragm in the motor valve the master valve 16 may bemoved through varying positions from its cutoff position' to its full open position according to the steam supply required in the drying rollers to effect the desired drying of the paper web passing thereabout.

Tension roll assembly Tension roll 14 extends across the entire width of the paper web being dried, being mounted at opposite ends in bearings 20. Said bearings are carried by the crank arms 21 fulcrurned on a stud 22 secured at the far end of the tension roll to the supporting bracket 23, and at the near end on the frame structure of the tension roll assembly. To maintain alignment of the crank arms 21 there is provided an overhead stabilizing assembly mounted on bearings 24 in which'there is pivotally mounted a rock shaft 25 secured to the upper arms 26 pivoted at their free ends to the adjustable connecting rods 27. The other ends of said connecting rods are connected to the free ends of the crank arms 21. The bearings 24 aresupported upon the framework of the paper making machine so that the rock shaft extends above or outside of the path of the paper being dried which passes between said shaft and the tension roll 14.

The entire tension roll assembly is carried by a bed plate 28 secured to the framework of the paper making machine at the position of the tension roll relative thereto. The bed plate carries an upstanding bracket 29 upon Which is mounted an air motor generally indicated at 30 for loading the tension roll as hereinafter described. Secured to the bed plate to extend outwardly therefrom thereis a bracket 31 carrying the pilot valve assembly generally indicated at 32; The near crank arm 21 is secured to a shaft 33 extending through the stud 22 and fixed mounting drum 34. Rotatably carried by said drum and keyed to said shaft there is a boss 35. Thus the boss 35 is caused to'oscillate by the tension roll 14 through the crank arms 21. Said boss carries an upstanding indicating finger 36 having a pointer 37 movable over the scale 38 fixed to the mounting drum. The pointer 37 indicates the relative position of the boss and tension roll as between medium weight paper at zero, light weight paper position toward the left and heavy weight paper position toward the right. For determining the proper tension with respect to the weight of paper the mounting drum and its boss are interconnected by an adjusting screw 39 adjustable by the tension roll adjust ing crank 40.

Adjustably secured to the tension roll boss 35 there is a pressure arm 41, the adjustment thereof relative to the boss being effected through the nut and slot adjustment indicated at 42. Said arm extends horizontally and laterally to a suitable distance from said boss with its free end moving relative to a fixed scale 43 secured to the base plate. Saidscale is provided with indicia from zero or neutral position at the center to indicating position numbers extending from opposite sides thereof. The position of the pressure arm 41 on said scale shows '4 the momentary location of the tension roll as well as the movement thereof. On each side of the pressure arm there are limit stops in the form of adjustable set screws 44 and 45, adjustable in suitable bosses secured to the base plate. Thus the maximum movement of the pressure arm, and consequently the tension roll may be limited to a prescribed variable position controlled by said limit stops, to control the minimum and maximum swing of said tension roll.

The air motor 30 applies tension to the tension roll, and in the tension direction against the paper web through the medium of a pressure head 46 which embraces the pressure arm 41 having a roller 47 engaging the upper edge thereof adjacent the boss 35. Said head is adjustably mounted on a threaded stem 48 which is threaded into a piston 49 operating in the, fixed cylinder 50. Downward pressure is exerted on the head of the piston by a cushioning spring taking the form of compression spring 51 mounting a cap 52 in the upper end thereof. Said cap is engaged by the lower end of a push rod 53 having its upper end bearing against an inner cap 54. Surrounding the push rod and extending between the inner cap and a fixed bottom cap 55 there is a compression spring 56. The bottom cap is secured in the housing 57 of the air motor 30 and bolted to the upper end of the cylinder 50 with'a spacing block 58 therebetween. Sealed between the inner cap 54 and an outer cap 59 there is a diaphragm 60, the outer edge of said diaphragm being sealed between a shoulder on the housing 57 and an inner cap 61. The upper end of the housing 57 of the air motor is provided with an air line connection 62 for receiving an air line fitting 63 from the line 64 through which air is introduced between the diaphragm and the cap 61. Said fitting is provided with a bleeder orifice 65 for permitting the air motor to have a cushion at all pressures.

Said air motor thereby loads the tension roll through engagement with the pressure arm 41, opposing the tension of the paper web engaged by the tension roll. T ightening of the paper web due to dryness balances off the air pressure in the air motor, the air pressure acting upon the diaphragm of the air motor through the line 64 being in effect controlled by a pressure reducing valve hereafter described and indicated at 117 in Fig. 2, and which pressure is indicated on pressure gauge 113.

Adjustably secured on the tension roll boss 35 there is provided a cam 66 having a predetermined curvature eccentric to the center of curvature of the tension roll shaft 33. Pivotally connected to the upper end of the cam there is an adjusting screw 67 adjustable in a boss 68 secured to the mounting drum 34. Pivotally connected to the lower end of the cam there is an adjusting screw 69 adjustable in the boss 70 on said drum by an, adjusting knob 71. The pilot valve assembly 32 is associated with and controlled by the cam 66 according to the oscillation of the tension roll mounting by boss 35.

The pilot valve assembly 32 is carried by the bracket 31 and includes a sleeve72 in which a bearing plug 73 is mounted in the end toward the cam. Slidably mounted in the bearing plug there is a plunger 74 carrying a cam follower comprising roller 75 riding upon the forward cam surface of the cam 66. Said plunger bears against one end of a diaphragm compression spring 76 which spring bears at its opposite end against a diaphragm head 77. Said head is clamped in sealing engagement with a diaphragm 78 by the sealing nut 79. Said sleeve 72 is provided with an air escape orifice 80. The diaphragm 78 is clamped against 'the bracket 31 in alignment with the sleeve 72 by a valve housing provided with a fluid passage chamber 81 communicating with an in'letfitting 82 on one side and an outlet fitting 83 on the other side. Separating the inlet and outlet sides of the chamber there is a plug 84 having an axial bore 85 leading from a valve seat recess 86 to the end thereof through which fluid may pass from one side of the chamber to the other. Within said recess 86 there is a valve member 87 biased by the compression spring 88 and fluid pressure thereon into seating in sealing position for closing the fluid passage through the bore 85. Abutting said valve member there is a square or fluted valve stem 89 slidable in said bore which extends into said chamber in abutting engagement with the bleeder valve 90.

The inlet fitting 82 of the valve chamber is connected to the air line 91. The outlet side of the chamber through fitting S3 is connected to the air line 92. The air line 91 is in indirect communication, as hereinafter described, with a source of air pressure at about 20 pounds. The line 92 is indirectly connected through controls hereinafter described, with the line 18 leading into the diaphragm motor 17. The action of the pilot valve assembly may be generally described as efiecting control or variation of the tension on the tension roll through the medium of the diaphragm motor 17. As the Web of paper changes its moisture content such as to cause the tension roll to fluctuate the cam 66 is caused to move relative to the cam follower 75 of the pilot valve assembly. This action causes the valve member 87 to open or close the air passage from the inlet side to the outlet side of the air chamber, and thereby increases or decreases the air pressure on the diaphragm motor 17. Through such variation in air pressure on the motor, the pin 47 acts upon the pressure arm 41 to vary the tension of the tension roller with respect to the paper Web.

Controlling instruments Operably associated with the tension roll assembly and steam motor valve 16 thereis a series of control instruments which may be remotely positioned at a convenient location, preferably mounted upon a panel 100. On the panel there is provided a pressure control instrument 101. This instrument carries a relay pressure control valve 102 and the mounting for a permanent record chart indicated at 103 for indicating and recording the drying pressure in the drying rolls as well as provide a permanent record of the output of the pilot valve assembly 32 which, when compared to laboratory tests, the numbers stamped on the chart, may be set up as the percent of moisture recording. After repeat runs of like weight of papers these can be transposed to percentage of moisture content of the paper. For this purpose there is provided a record pen 104 which records the moisture and moisture variation of the paper as measured by the tension rolls. The chart is also associated with a steam pressure recording pen 106 which records the actual steam pressure of the steam supply header usually indicated by red ink. Pen 106 is controlled by pressure controller 102 as set by pressure setting knob 105. In event of a paper break, by means of an electric eye system hereinafter described, the pen 106 is automatically governed by controller 102 and other mediums. At 107, 107a and connected with the pens through suitable linkage there is provided a pair of Bourdon tubes, one for each. At 108 there is provided a proportional band setting knob which controls the sensitivity of the pressure controller 102.

Below the controlling panel 101 there are provided the following instruments: At 109 there is a pressure gauge indicating the air pressure supplied to the pressure controller 102 and also to the pilot valve assembly 32 through its line 91. At 110 there is a pressure gauge indicating the mill supply pressure which flows through line 112 to supply pressure reducing valves 114 and 117, the reduced pressure being indicated thereby. At 113 there is a pressure gauge indicating the air pressure loading the tension roll through the valve 117 and air motor 30. The pressure reducing valve 114 reduces the pressure indicated by gauge 109 supplying pressure to the pressure controller 102, as well as the pressure actuated instruments and the pilot valve 32 through the line 91. Said reducing valve is also connected with the manual closed position of the 4-way routing valve 115, as hereinafter described. At 116 there is a 3-way routing valve for selecting between single and dual operations as hereinafter described. At 117 there is the reducing valve for the air loading of the air motor 30 through the line 64.

The pressure gauges 118, 119 and 120 are provided for synchronizing the tension control with pressure control, for example, when first starting or warming up the machine after a shut down or a radical change in the basic weight or thickness of the paper which is being dried. When the web of paper is oil the dryers the tension control. part of the system is inoperative. The operator sets the 4-way routing valve on the panel board to pressure control (Fig. 5) when the paper is off the dryers and when first brought over the dryers, a sample of the paper having been taken to indicate the moisture content. By manually adjusting the pressure controlling device until the correct moisture is obtained it is then easy to make the adjustments on the pressure reducing valve 117 which connects to the air loading cylinder 30 through line 64. The valve 117 is adjusted, the pressure being indicated on gauge 113, until cam 66 is centered relative to follower 75 of the pilot valve 32 and the pressure indicated on gauge (which indicates the outlet or output pressure from pilot valve 32) equals the pressure shown on gauges 113, 119. After the pressure on gauge 120 is thus synchronized with pressures at 118, 119, the operator turns the 4-way routing valve 115 to tension control, whereupon the automatic tension control is in readiness to take over. Such tension phase of the control may continue until a break in the paper Web occurs, whereupon the electric eye phase or automatic cut out system takes over as hereinafter described.

A location gauge 120a (Fig. l) is provided in said line, corresponding to gauge 120. These gauges 120 and 120a indicate the tension roll actuated pilot valve air presure (lines 18 and 92), which pressure controls the moisture recording by pen 104.

At 121 there is a pressure gauge for indicating the steam pressure in the steam supply header to the dryers. At 122 there is provided a dial type thermometer indicating the temperautre of the steam in the steam supply to the dryers. At 123 there is a pressure gauge indicating the pressure on the return header from the dryers. At 124 there is provided a connecting block through which the several lines lead from the motor valve and tension roll assembly tocorresponding lines leading to the several instruments above identified.

Into the fitting 124 there is connected the line 112 leading from the fluid source into line 1 of the panel. Line 2 of the panel is connected with the line 92 leading out of the pilot valve assembly 32. Line 3 of the panel leads to the line 64 of the air motor 30. Line 4 of the panel leads to a test cock 125 connected with the pressure gauge 123. The line 5 of the panel is connected with line 18 of the motor valve 17. Line 6 of the panel is connected with the inlet line 91 of the pilot valve assembly.

A steam sampling line 15a leads from the steam pressure supply header 15 of the steam valve 16 through a shut ofi valve 126 for connection with the pressure gauge 121, thermometer 122, pressure gauge 123 and discharge valve 127 to a return header.

t the point indicated by da in the line leading to valve 127 there is an orifice similar to that used on drying rolls or cylinders. This orifice is approximately A diameter and is protected by fine mesh screen in a T fitting. This restricts the flow through the sampling header to a minimum to prevent the pressure from building up in the line which enters discharge valve 127 and line 15b, which is a /2 pipe of several times greater area than the restriction. This permits a reading of the pressure in line 15b and is not afiected by the pressure in the sampling header entering through valve 126. The

pressure in line 15b which is attached to the return header, and is the drainage of the paper machine dryers, has a very important function. To illustrate the convenience of this particular pressure in the return line of the paper machine dryers it may be noted that each drum or dryer is equipped with the conventional syphon pipe in one form or the other. This passes through the dryer journal and is deflected downward towards the bottom of the dryer to within A" to /2" of the inside diameter of each of the dryers. In order to affect drainage a differential in pressure is necessary which would be the pressure differential shown on gauges 121, line 15a, and the pressure shown on gauge 123, line 15b. This difierential in pressure is necessary to evacuate the condensate and remove the air and non condensable gases from the dryers. Thus, the gauges 121 and 123 permit the operator to quickly ascertain the pressure differential which indicates the performance of the drainage system, a very important factor in connection with the drying of paper and the high efficiency of the paper machine.

Thermometer 122 indicates whether the steam temperature is of the right quality and is equal to the temperature of saturated steam or if the steam is super heated. If superheated, it is very detrimental in the drying of paper. If the temperature is depressed below that of saturated steam it indicates that the quality of steam to the dryers is very low and that the highest efliciency is not obtained. If the temperature gauge 122 indicates super heat or above the temperature of saturated steam this causes uneven drying across the web of paper. These two gauges 121, 123 and thermometer 122 permits the operators to get a quick analysis of the steam being supplied to the dryers; i. e., if there is sufficient diflerential in pressure between the supply and return header to evacuate the condensate from the dryer cylinders, and also effect the removal of air and non con densable gases.

The air from the source S leads through the line 1 in the panel for connection with reducing valve 11.4, pressure gauge 109 and reducing valve 117 as indicated in the direction of the arrows. Line 2 in the panel leads in the direction of the arrows from the pilot valve assembly outlet line 92 to the 3-Way routing valve 116, the 4-way routing valve 115 and the Bourdon tube 107a. It also passes through the solenoid valve 132. Air line 3 of the panel leads from the reducing valve 117 into which the source of air pressure is directed from line 1, also actuating the pressure gauge 113, controlling the air pressure loading on the tension roll through line 64 of the air motor 30. Line 5 of the panel leads from the 4-way routing valve 115 and pressure gauge 119 to the line 18 connected with the diaphragm actuating motor valve 17. Line 6 of the panel leads from the reducing valve 114 in the direction of the arrows, and also from the pressure gauge 189 to the intake line 91 connected with the pilot valve assembly.

The outlet side of the pressure controller 162 is connected with the line 7 which leads to one of the connections in routing valve 115. A branch line 7 also leads to the 3-way routing valve 116. A further branch line 7 leads to the pressure gauge 118. The diverting solenoid valve 132 in line 2 is adapted to divert pressure from line 2 to line 7 upon a paper break. A line 8 connects the pressure controller 102 with the nozzle assembly of the pressure setting knob 105 and proportional hand setting knob 108. A steamfeeder line 9 leads in the direction of the arrows from the valve 126 in line a directly to the Bourdon tube 107 of the pen 106.

The control system The above described pressure and moisture control system is designed to provide a complete moisture control or pressure control or the combination of the two, for the paper passing over the paper machine. By strategical- 1y locating the tension roll, running the full width of the machine dryers, the routing and controlling of the compressed air from the inlet of the instrument cabinet through the various controls to the diaphragm motor valve 17, not only effective drying control may be maintained, but the complete system may be operated from a conveniently and remotely located control box having easy to read dials and readily operative routing and set pressure reducing valves.

The tension roll 14 positions the cam 66 according to the moisture content of the paper, which cam in turn actuates the pilot valve 32 having the built-in bleeder which eliminates all weights, pulleys, jack chain and differential springs heretofore employed.

As the angle of this cam is increased it permits greater pilot valve movement by a lesser tension roll travel. The carn requires a lesser angle for the heavier weight papers such as heavy board, printing and cardboard due to the greater expansion and contraction of these Papers with a minimum of moisture content change. Decreasing the angle of this cam allows a greater tension roll movement in proportion to the movement of the pilot valve. By increasing the tension roll movement in relation to the movement of the pilot valve it prevents cycling or hunting brought about by the air supply to the steam control valve 16 as the web of the paper changes its moisture content.

Thus, a streamlined air loaded diaphragm system is provided wherein the tension roll may be positioned readily and quickly by merely operating the crank 40. Furthermore, a built-in pressure release system has been provided to protect the pressure control instrument and pilot valve from excessive air pressure due to failure of a PRV or pressure relief valve through possible negligence of an operator. It may further be noted that the entire system takes up a minimum of valuable space along the tending side of the paper machine.

Operation In starting up the control system, when all lines are connected and installation completed, the valve 114 (Fig. 2) or pressure regulation valve is turned clockwise until the pressure gauge 109 indicates the desired p. s. i., for example, 17 p. s. i. This supplies the pressure control instrument and pilot valve 32 simultaneously with the necessary operating air pressure. The routing valve 115 (Fig. 5) is then turned from its ofi position (position A) to its pressure control position, as shown at position B. The 3-way routing valve 116 (Fig. 6) is set at its manual position A. The diaphragm motor valve 17 will then open the main steam valve 16 which remains open until the pressure setting by the pressure controller 102 is reached by the actual pressure in the supply header, as indicated by the pressure indicating pen 106 and by the gauge 121. Relative temperature of the steam in the supply header will be registered by the thermometer 122. Pressure of the return header will be indicated by the gauge 123. A glance at the instruments will show the difierential pressure in the supply and return headers, i. e., the difference between the steam in the supply header (gauge 123) and that in the return header (gauge 121). If it is desirous to run on pressure control alone, the proper settings have now been made.

To shift the system from automatic =Pressure Control to automatic Tension Control, there is involved the cutting out of the pressure control instrument and the cutting in of the pilot valve 32 which is acuated by movement of the tension roll, in turn actuated by the moisture content of the sheet engaged thereby. This rerouting of the air pressure is accomplished by the movement of the routing valve 115 from the position at B to the position at C. In this position the diaphragm motor valve 17 controlling the introduction of steam to the steam header, is commanded by the pilot valve 32. Thus, the pilot valve receives its commands from the moisture content of the paper. If the paper becomes too moist, the ten- 9 sion roll moves into the sheet and the pilot valve tends to close, the bleeder valve 90 being opened to release pressure from the diaphragm chamber of the motor 17, which, through the biasing of the block 19, tends to open the main steam valve 16. If the paper becomes too dry, the sheet moves the tension roll in the opposite direction, whereupon the bleeder valve 90 is closed and the pilot member 87 is open, sending air pressure to the motor valve 17 tend-ing to close the main valve 16. On a reversley acting valve installation, however, the action of the pilot valve .and the main valve will be just the reverse.

To prevent a hunting action or flutter of the tension roll, the air motor 30 is introduced into the system to transfer air pressure, as controlled by the pilot valve 32 and the pressure controller valve 102, to the tension roll through engagement with the pressure arm 41. Thus, the tension roll is weighted indirectly by the pressure exerted on the diaphragm 60 of the air motor through lines 3, 64 controlled by the reducing valve 117 according to the pressure loading to be applied to the tension roll, as indicated by the gauge 113. Such pressure loading through the motor valve is applied through the dual spring action of the springs 51, 56, the respective tensions of which may be adjusted. It should be noted, however, that there is no direct or positive action between the deflection of the diaphragm 60 and the movement of the pressure head 46 on the pressure arm 41 of the tension roll. Thus, any hunting action as between the tension roll and the loading pressure thereof is absorbed by the dual action of said springs under pneumatic pressure.

Due to the weight of the tension roll and its component parts, it is necessary to compensate therefore in order to pick up sensitive fluctuations of the sheet. The air loading diaphragm of the air motor 30 performs this function .as opposed to the usual provisions of counterweights or the like. Thus, the opposing thrust or counterweight may be changed quickly and conveniently from the remote instrument panel. To adjust the pressure on the diaphragm of the air motor, the valve 117 is turned clockwise to increase pressure and counterclockwise to decrease pressure. The reading of the actual air pressure on the air motor-serving as a counterweight for the tension rollmay be taken from the gauge 113. Pressure to the air motor should be increased until the arm 41 of the tension roll is approximately in the center of the scale 43. This indicates that the tension roll is counterweighted to the right amount for sensitive transfer of the moisture condition of the sheet to the pilot valve. At the same time variances in the weights of paper being run may be compensated for through the operation of the crank 40 to move the pointer 37 on the dial 38 to the left for lightweight and to the right for heavy weight paper. This adjustment and the setting of the proper air pressure to bring the arm 41 at zero position on the scale 43 will provide the proper balancing and counterweighting of the tension roll according to the weight of the paper being run.

Pressure control phase interconnecting the several instruments there is provided interconnecting air lines as follows: Line 6 in addition to leading from reducing valve 114 and pressure gauge 19 leads into the 4-way routing valve 115. The outlet side of the pressure controller 102 is com nected with line 7 which leads to one of the connections in routing valve 115. A branch line 7 also leads to the 3way routing valve 116. A further branch line 7 also leads to the pressure gauge 113. A line 8 connects the pressure controller 102 with the nozzle assembly of the pressure setting knob 105 and proportioning hand setting knob ltlS. A Steam feeler line 9 leads in the direction of the arrows from the valve 126 in line 15a directly to the Bourdon tube 107 of the pen units. The controlled air pressure from valve 102 passes down through line 7 in the direction of the arrow. The air pressure is indicated on gauge 118 while passing through the 4-way routing valve into line 5 and through line 18 to dia phragm motor valve 16 and 17.

Referring to Fig. 5, when the 4-way routing valve is set as at B, the 3-way valve 116 is set in closed position. When the 4-way valve is thus set, the controlling air pressure from pressure controller 102 passes down through the routing valve to line 5 and through line 18 to the diaphragm motor control valve 16 and 17.

Tension control phnlre Referring to Fig. 5, the 4-way routing valve 115 is set in position C for tension control, and the 3-way valve 116 remains in its closed position. When the controls are in this position the pressure control phase is inoperative as line 7 is blanked off. The controlled air line from the pilot valve 32, which is actuated by the tension roll, through line 92 to air line 2 of the panel is then connected through the 4-way valve with line 5, 18 directly to diaphragm motor 16, 17. When and if the web of paper breaks ahead of the tension roll, it will permit the pressure on pressure arm 41 to drop, allowing cam 66 to close the air passage through the pilot valve 32 which if not corrected would allow the diaphragm motor 17 of the steam control valve to go to the wide open position, causing excessive pressure in the drying cylinders. If such action is not checked and immediately corrected, it would cause damage to the cylinders or over drying of the paper when the sheet is brought over again. The electric eye 130, 131 or electric phase as hereinafter described will automatically close off or reset the steam valve by either closing off the valve entirely or resetting it through the pressure controlling device 1G2 at the pressure desired during the down time or period of the paper machine.

Electric eye phase of automatic break shut ofi In event of breakage of the paper, the routing valve 115 may be immediately turned manually to an off position (no-t shown). To provide a quick shut off by placing air pressure on the diaphragm valve 17 this lever arrangement manually operated is also advantageous if for any reason it should be desired to shut off the entire steam supply to the dryers. But there is also provided in the rerouting of valve 115 provision for automatically maintaining any predetermined constant pressure desired during the period the paper is off the machine through the medium of the pressure controlling device heretofore described.

However, to eliminate operator failure in this respect there is provided any suitable electric circuit control such asa light sensitive cell Fig. 8 position on one side of the web and the usual light source 131 on the other side. The cell remains negative as long as the paper going over the dryers or cylinders but in case of a break the cell becomes energized from the light source to close a circuit (not shown) through the solenoid control valve 132.

In event of break-age of the web of paper ahead of the tension roll, there is no impulse or activating medium to control the air or steam supply pressure as heretofore described. The electric eye or other means of controlling an electric circuit indicating web breakage operates solenoid valve 132 in line 2. In its normal position said valve is open to unrestricted flow of air from the tension roll pilot valve 32 through line 2 and 4-way valve 115 when set in position C (Fig. 5). In event of breakage, said valve is shifted to thereby divert air pressure through lines 5 and 18 to diaphragm motor valve 16, 17.

The steam pressure to the dryers will thereupon be controlled through control of the pressure controlling device 102 as heretofore described under the Pressure Control Phase. When the paper web is again brought over the dryers past the tension roll causing a break in the circuit to the solenoid valve, it will shift back to its normal position and automatically return the controlling 1 1 device 102 to its normal operation under the automatic Tension Control Phase.

Manual control phase In case of mechanical failure of either or both of the pressure or tension control devices, a manual control is provided as shown in Fig. 5, position A, which routes the air or fluid controlling medium from line 6 to line 5. A graduated scale may be provided on the face of valve 115 in increments from O to 4. Position indicates that the diaphragm motor valve 16 is in wide open position, and position 1 indicates that it is A closed; position 2 indicates that it is /2 closed; position 3 indicates that it is /1 closed; and position 4 indicates that the steam control valve 16 is completely closed. If the operator wishes to close the diaphragm motor valve quickly, he turns the lever on routing valve 115 to position A (Fig. 5), which connects the air pressure from line 6 to line 5.

Dual control phase The feature of the dual operations lies in its quality control of the sheet by two means--i. e., the pressure control instrument and the tension roll. While the pressure control instrument maintains a set steam pressure on the machine, the tension roll dominates so as to take over in extreme variances of moistness or dryness. Once compensating for extremities, it turns control of the system back to the pressure control instrument which is a more stable guardian of the control pressure. However, the pressure control instrument has no feel of the actual sheet in respect to moisture content. Furthermore, a more sensitive operation may be attained through the medium of the pilot valve if another agent is handling an accurate pressure on the dryers at all times, for example, the air motor 30. The air motor maintains the diaphragm motor valve 17 in a throttling valve position when the pilot valve does make a demand on the diaphragm motor valve. Movement to fulfill these demands is thereby limited.

To set the system on dual pressure-tension roll control, the 3-way routing valve 116 (Fig. 6) is turned to Dual Control operation, as indicated at position B, and the 4-way routing valve 115 (Fig. 5) is turned to the position indicated at B which coincides with its position used for automatic pressure control. The system will then be operating on dual pressure-moisture control, jointly bringing into the system the pressure controller valve 102 and the pilot valve 32. Thus, the pressure controller valve maintains the prescribed pressure, whereas the pilot valve through the medium of the tension roll actuated cam 66 functions to compensate for variances in moisture content of the paper.

The 3-way valve 116 is normally positioned for the pressure control and tension control phases, preventing the passage of air or fluid from line 7 to line 2, 92. When in position A (Fig. 6) there is no passage through this valve. When the 3-way valve 116 is turned to the operating position for dual control, the ports therethrough are opened from line 7 to line 2. However, the 4-way valve 115 has a special setting and function in connection with valve 116 for the purpose of this dual arrangement. When operating with dual control, with the setting on the 4-way valve 115 as indicated in position B (Fig. 5), the line 7 is open to line 5, and the 3-Way valve 116 is open for passage from line 7 to line 2. The flow of air or fluid with such dual control setting can be in either direction through the 3-way valve 116. For example, this occurs when the pressure setting portion of the control and the tension setting are synchronized as indicated and heretofore described, and the pressure on gauges 118 and 119 and 120 are the same, and there has been the prescribed setting for dual control.

Assuming that the tension roll pilot valve 32 starts to increase the steam pressure to the drying system by lowering the air'pressure on the diaphragm motor valve 16 12 through line 5, the pressure in line 15 starts to decrease which in turn acts on the Bourdon tube 107. This action in turn starts to close an air leakaway port which is provided on the end of line 8 actuated by a flapper attached to the control mechanism and 108. By closing the leakaway of pressure in line 8 it affects the pressure control 102 which causes added air pressure to be built up in line 7 which in turn allows the pressure to build up through line 7 and the 4-way valve to the motor diaphragm line 5, 18. The reverse action takes place when the tension roll starts to move in the opposite direction to open the pilot valve 32, increasing air pressure in line 2. The steam pressure then decreases in the supply to the drying system. This pressure through line 15a gives the impulse to the Bourdon tube 107 to start to decrease the air pressure in line 8 by increasing the air leakaway through line 8 which is actuated by the Bourdon tube. This action causes a resetting of the diaphragm motor valve. By adjusting the throttling band of the control 102, the plus or minus pressure can be increased or decreased to take care of the normal fluctuation as hereinafter described.

The purpose of the dual control is as follows: It has been found that on heavy papers such as board, there is a tendency when operating with the tension roll only for control to cycle or hunt causing excess steam pressure variation in the drying system. This is brought about by momentary variation in the basic weight of the paper, uneven thickness or other variables which are usually momentary. When these conditions are gauged by the tension roll, the sheet goes back to its normal position for normal drying pressure. However, if the tension roll is permitted to act in response to these momentary variations especially on a machine havinga large number of dryers, there is a tendency to throw the load or drying pressure and vary the back pressure on the turbine to the extent of causing extreme variation in the drying conditions on the machine. Therefore, it is desirable to provide such method of stabilizing the pressure in conjunction with the tension control, and control the plus or minus in pressure as is required to take care of such fluctuation.

Recording chart In Fig. 7 there is shown chart 103 of the recording instrument having radially disposed hour indicating lines and a series of concentric pressure and moisture indicating lines. On the chart the outer Zigzag line is drawn by the pen 104 which indicates the moisture content of the paper being dried. Having determined the degree of moisture required for the particular sheet of paper being run, the position of the recording pen 104 is noted and as indicated and recorded in outer line 104a, 10%. The pen records the variation in moisture brought about by the movement of the tension roll and indicates the moisture variation. Oncethe correct moisture is established and the position of pen 104 is noted, the degree of moisture variation will be recorded and when again returning to this same Weight and type of sheet a duplicate setting can be made to secure the same moisture content. It is desirable that this line fluctuate at a minimum. Wherein extreme fluctuations are indicated as at 1047;, there has been a paper break or some other interrupting factor. The steam pressure required to maintain a steady moisture content, as indicated by the line 104a, is indicated by the line 106a through the medium of the recording pen 106. This line indicates the varying pounds pressure determined by the position of the master valve 316 through control of the motor valve 17 for maintaining the steady predetermined moisture content of the paper.

The controller 102 is connected to the pen 196 and Bourdon tube 107. Pen 104 is connected to a second Bourdon tube 107a. This latter Bourdon tube controls pen 104 but has no other function than to record the pressure as herein described, and indicates the pressure through the Bourdon tube. The Bourdon tube 104a gets 13 its impulse from air pressure in line 2 which is theoutput pressure from the tension rollpilot valve 32 through lines 2, 92.

The invention claimed is:

l. A control system for paper machines having drying rolls for drying paper passing thereover, including a steam line supplying steam to said rolls, a main steam control valve in said line, a fluid pressure actuated motor controlling said valve, a tension roll engaging a Web of paper passing over said drying rolls, a fluid pressure line con nected with said motor having a source of fluid pressure, a valve in said fluid pressure line for setting a predetermined pressure therein, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said motor according to the moisture content of the paper as communicated to said tension roll, a variable pitch cam movable with said tension roll operably connected with said pilot valve for the actuation thereof and means for varying the pitch of said cam.

2. A control system for paper machines having drying rolls for drying paper passing thereover, including a steam line supplying steam to said rolls, a main steam control valve in said line, a pressure actuated motor controlling said valve, a tension roll engaging a Web of paper passing over said drying rolls, a fluid pressure line connected with said motor having a source of fluid pressure, a pres sure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a chart recording instrument connected with said steam line and fluid pressure line for permanently recording the steam pressure in said steam line and the pressure in said fluid pressure line, the latter indicating moisture content of the paper through fluctuation of said fluid pressure, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said motor according to the moisture content of the paper as communicated to said tension roll, and a routing valve interposed in said line between said pressure control valve and said pilot valve for selectively routing the fluid pressure from said pressure control valve to said motor to establish automatic pressure control thereof when in another position and from said pilot valve to said motor to establish automatic tension roll control thereof.

3. A control system for paper machines having drying rolls for drying paper passing thereover, including a steam line supplying steam to said rolls, a main steam control valve in said line, a pressure actuated motor controlling said valve, a tension roll engaging a web of paper passing over said drying rolls, a fluid pressure line connected with said motor having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a chart recording instrument connected with said fluid pressure line for permanently recording the steam pressure in said steam line and the pressure in said fluid pressure line, the latter indicating moisture content of the paper through fluctuation of said fluid pressure, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said motor according to the moisture content of the paper as communicated to said tension roll, a routing valve interposed in said line between pressure control valve and said pilot valve for selectively routing the predetermined fluid pressure from said automatic pressure control valve to said motor to establish a predetermined pressure control thereof when in one position and from said pilot valve to said motor to establish tension roll control thereof when in another position, said routing valve being movable to an additional selective position for manually varying the fluid pressure directly from said source to said motor at predetermined variances in pressure and to another selective position to exhaust fluid pressure from said motor to atmosphere, and a second routing valve interposed in said line between said first routing valve and pilot valve selectively movable to connect both said pilot valve and pressure control valve with said motor through said firstmentioned routing valve.

4. A pressure control system for paper machines having drying rolls for drying paper passing thereover including a steam supply line for said rolls, a pressure actuated steam control valve in said line, a tension roll engaging a web of paper passing over said rolls, a fluid pressure line connected with said valve having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said pressure actuated stearn valve according to the moisture content of the paper as communicated to said tension roll, and a routing valve interposed in said line between said pressure control valve and said pilot valve operable to selectively cut said pilot valve out of said pressure line for effecting control of the pressure on said pressure actuated valve by said pressure control valve, when in one position, and out said tension roll controlled pilot valve into said line to effect said control thereby when in the other position.

5. A pressure control system for paper machines having drying rolls for drying paper passing thereover including a steam supply line for said rolls, a pressure actuated steam control valve in said line, a tension roll engaging a web of paper passing over said rolls, a fluid pressure line connected with said valve having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said pressure actuated steam valve according to the moisture content of the paper as communicated to said tension roll, a routing valve interposed in said line between said pressure control valve and said pilot valve operable to selectively cut said pilot valve out of said pressure line for effecting control of the pressure on said pressure actuated valve by said pressure control valve, when in one position, and cut said tension roll controlled pilot valve into said line to effect said control thereby when in the other position, and a second routing valve interposed in said line between said first routing valve and pilot valve operable to selectively connect both said pressure control valve and said pilot: valve into said line leading to said steam control valve for jointly effecting control thereof by predetermined pressure and tension roll control.

6. A pressurecontrol system for paper machines having drying rolls for drying paper passing thereover including a steam supply line for said rolls, a pressure actuated steam control valve in said line, a tension roll engaging a web of paper passing over said rolls, a fluid pressure line connected with said valve having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said pressure actuated steam valve according to the moisture content of the paper as communicated to said tension roll, a record chart, a recording pen movable relative to said chart operable to record the steam pressure thereon actuated by the pressure in said line as controlled by said pressure control valve, and a second recording pen movable relative to said chart operable to record the moisture content of the paper on said chart actuated by the pressure in said pressure line and operably connected with said pilot valve whereby its recordings will be controlled through said pilot valve by said tension roll.

7. A pressure control system for paper machines having drying rolls for drying paper passing thereover including a steam supply line for said rolls, a pressure actuated steam control valve in said line, a tension roll engaging a web of paper passing over said rolls, a fluid pressure line connected with said valve having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said pressure actuated steam valve according to the moisture content of the paper as communicated to said tension roll, a routing valve interposed in said line between said pressure control valve and said pilot valve operable to selectively cut said pilot valve into and out of said pressure line for eflfecting control of the pressure on said pressure actuated valve by said pressure control valve, when in one position, and by said tension roll controlled pilot valve when in the other position, a record chart, a recording pen for recording the steam pressure on said chart actuated by the pressure in said line as controlled by said pressure control valve, and a second recording pin for recording the moisture content of the paper on said chart connected in said pressure line and operably connected with said pilot valve whereby its recordings will be controlled through said pilot valve by said tension roll.

8. A pressure control system for paper machines having drying rolls for drying paper passing thereover including a steam supply line for said rolls, a pressure actuated steam control valve in said line, a tention roll engaging a web of paper passing over said rolls, a fluid pressure line connected with said valve having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a pressure reducing valve in said pressure line for manually determining the pressure control by said pressure control valve, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said pressure actuated steam valve according to the moisture content of the paper as communicated to said tension roll, and a routing valve interposed in said line between said pressure control and pressure reducing valves and said pilot valve operable in one position to connect said pressure reducing valve with said steam control valve, when in a second position to connect said pressure control valve with said steam control valve, and when in a third position to connect said pilot valve with said steam control valve.

9. A pressure control system for paper machines having drying rolls for drying paper passing thereover including a steam supply line for said rolls, a pressure actuated steam control valve in said line, a tension roll engaginga web of paper passing over said rolls, a fluid pressure line connected with said valve having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a pressure reducing valve in said pressure line for manually determining the pressure control by said pressure control valve, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said pressure actuated steam valve according to the moisture content of the paper as communicated to said tension roll, and a routing valve interposed in said line between said control and reducing valves and said pilot valve operable in one position to connect said control and reducing valves with said steam control valve, when in a second position to connect said pressure control valve with said steam control valve and when in a third position to connect said pilot valve with said steam control valve, and a second routing valve interposed in said line between said first mentioned routing valve and said pilot valve operably connecting the pressure line from said pressure control and reducing valves with the pressure line from said pilot valve operable with said first mentioned routing valve to jointly control said steam control valve by the predetermined pressure from said control and reducing valves and the tension roll controlled pressure from said pilot valve.

10. A pressure control system for paper machines having drying rolls for drying paper passing thereover including a steam supply line for said rolls, a pressure actuated steam control valve in said line, a tension roll engaging a Web of paper passing over said rolls, a fluid pressure line connected with said valve having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting and maintaining a predetermined pressure therein, a tension roll actuated pilot valve connected in said fluid pressure line operable to vary the pressure on said pressure actuated steam valve according to the moisture content of the paper as communicated to said tension roll, a routing valve interposed in said line between said control and pilot valves operable to selectively cut said pilot valve into and out of said pressure line for eflecting control of the pressure on said pressure actuated valve by said pressure control valve, when in one position, and by said tension roll controlled pilot valve when in the other position, a solenoid valve in said line normally open for passage of pressure from said pilot valve and control valve to said routing valve, said solenoid valve upon being energized closing off the pressure from said pilot valve to said routing valve, and electric control means governed by a paper break on said drying rolls electrically connected with said solenoid valve and a source of energy operable to energize said solenoid valve in the event of a break to render effective and maintain the predetermined pressure governed by said pressure control valve and prevent variation in pressure under control of said pilot valve and tension roll, whereby when the said routing valve may be positioned in its last mentioned position it will automatically become effective only in its first mentioned position to maintain said predetermined pressure during a paper break, irrespective of the tension roll control pressure through said pilot valve.

11. A control system for paper machines having drying rolls for drying paper passing thereover, including a steam line supplying steam to said rolls, a main steam control valve in said line, a fluid pressure actuated motor controlling said valve, a tension roll engaging a Web of paper passing over said drying rolls, a fluid pressure line connected with said motor having a source of fluid pressure, a pressure control valve in said fluid pressure line for setting a predetermined pressure therein, an air motor having a spring biased diaphragm, an air line connecting said fluid pressure line with said diaphragm, and a cushioning spring interposed between said diaphragm and tension roll adjustably connected therewith for yieldingly maintaining said predetermined fluid pressure thereon.

12. A control system for paper machines having drying rolls for drying a paper Web passing thereover, including a steam line to supply steam to said rolls, a main steam control valve in said line, a fluid pressure actuated motor References Cited in the file of this patent UNITED STATES PATENTS 285,954 Barry Oct. 2, 1883 448,181 Dillon Mar. 10, 1891 1,545,638 Clay July 14, 1925 2,120,079 Stickle June 7, 1938 2,122,362 Stanton June 28, 1938 2,469,915 Capstafl May 10, 1949

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US285954 *2 Oct 1883 baeet
US448181 *19 Sep 189010 Mar 1891F Onedillon
US1545638 *6 Jan 192314 Jul 1925Reeves Pulley CoAutomatic speed regulation
US2120079 *2 Oct 19367 Jun 1938Stickle Steam Specialties CompAutomatic steam control for paper machines
US2122362 *30 Apr 193528 Jun 1938Eldon MacleodControl mechanism for paper making machines
US2469915 *20 Apr 194510 May 1949Eastman Kodak CoApparatus for handling motionpicture film
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3016622 *10 Jul 195716 Jan 1962Kimberly Clark CoControl system for paper machine driers
US8069582 *24 Dec 20086 Dec 2011Daewoo Electronics CorporationDryer
Classifications
U.S. Classification34/556, 162/255, 118/60
International ClassificationD21G9/00
Cooperative ClassificationD21G9/0036
European ClassificationD21G9/00B6