US1882991A

US1882991A - Method of and apparatus for delivering pulp stock at constant tonnage rate

Info

Publication number: US1882991A
Application number: US495599A
Authority: US
Inventors: Milton O Schur
Original assignee: Brown Co
Current assignee: Brown Co
Priority date: 1930-11-14
Filing date: 1930-11-14
Publication date: 1932-10-18
Anticipated expiration: 1949-10-18

Description

Oct. 18, M o sc R 1,882,991

METHOD OF AND APiARlxTUs FOR DELIVERING PULP STOCK AT CONSTANT TONNAGE RATE Y Filed Nov. 14, 19so 4 Sheets-Sheet 1 Oct. 18, 1932. M. o. SCHUR 1,882,991 METHOD OF AND APPARATUS FOR DELIVERING PULP STOCK AT CONSTANT TONNAGE RATE Filed Nov. 14, 1930 4 Sheets-Sheet, 2

I (@0672)?? ZZZ/fix JzZzzm WWW Get. 18, 1932. M. o. SCHUR v1,882,991

- METHOD OF AND APPARATUS FOR DELIVERING PULP; 1

STOCK AT CONSTANT TONNAGE RATE Filed Nov. 14, 1930 4 Sheets-Sheet "3 Oct. 18, 1932. M. o. SCHUR 1,882,991

METHOD OF AND APPARATUS FOR DEL]:VERING' PULP STOCK AT CONSTANT TONNAGE RATE Filed Nov. 14, 1950 4 Sheets-Sheet 4 Patented Oct. 118, 1932 UNITED STATES PATENT OFFICE MILTON O. SCHUR, OE BERLIN, NEW HAMPSHIRE, ASSIGNOR TO BROWN COMPANY, OF

- BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE mnrnon or AND APPARATUS ron DELIVERING PULP sroox AT RATE n CONSTANT TONNAGE Application filed November 14, 1930. Serial No. 495,599.

This invention relates to a method of and apparatus for delivering pulp stock at a constant tonnage rate.

i In the maufacture of several articles or substances from wood pulp it is highly important that the pulp be supplied at a constant tonnage rate, that is, that the dry weight of the pulp delivered for a unit of time should be substantially constant with a very small maximum variation. This is especially important where the pulp is to be treated with measured quantities of chemicals. It is a relatively simple matter to supply a constant volume of pulp stock. By regulating the consistency of such stock so as automatically to maintain the consistency substantially uniform, \a substantially constant tonnage rate of delivery can be obtained. In combining the two steps so as to obtain a constant volume rate of stock having a constant consistency, several practical difliculties are encountered. It is an object of this invention to provide apparatus which avoids such difficulties and which is capable of delivering pulp with only slight variations in the tonnage rate.

The present invention includes improvements over the subject matter of my Patent No. 1,744,145 granted January 21, 1930. In ordinary mill practice the consistency of pulp stock supplied from storage tanks is liable to vary from time to time owing to a variety of causes such for example as local dilution caused occansionally by Wash water used in cleaning out the beater. Furthermore, one

days run of stock may differ materially in consistency from that of another day so that it is necessary to regulate the consistency of stock supply in order to insure uniformity. To this end the stock which is supplied from the beater must be thicker than that which is delivered at a constant tonnage rate since the consistency is, according to the present invention, regulated by diluting the supplied stock and controlling the rate of addition of the diluted water. In the apparatus described in my Patent No. 1,744,145, diluting Water is mixed with the supply stream of stock, the diluted stock being pumped into a vat or tank from which it is metered at a constant rate. The excess diluted-stock escapes over a suitable dam and fiows back to the supply tank from which it was pumped; This results in a dilution of the stock in the supply tank.

at which it was metered therefrom. The regulating valve, besides obviating unnecessary variation in the consistency ofthe supply stream of stock also eilects a considerable saving in the power required to drive the p pump for the supply stream. Pumps of the centrifugal type are frequently used for streams of pulp stock. It is characteristic of this type of pump that when working against a closed valve, less power is required to operate the motor of the pump than when a valve is open, this being due to the fact that when no liquid is being discharger from the pump, the liquid within the pump casing merely flows around with the paddles. When, however, the valve is open, velocity must be imparted to the incoming stream of liquid to discharge it through the discharge pipe. This requires considerably more power than that required for merely maintaining a circular flow of a. small amount of liquid within the ing vat is diverted and caused to flow past the feeler of the regulator at substantially constant speed' This makes possible a considerable simplification of the apparatus. A constant velocity of flow of the sampling ing device driven at constant speed. The.

metering device may be a type widely used for feeding pul stock at a constant volume rate by means a wheel revolving on a horizontal axis to present to the pool successive com artments formed by a number a of pad es. ,To avoid the sticking of pulp in the angles between successive addles in a wheel of small size such as is suitable for use in a sampling stream, I may block off or fill.

the space between paddles for a short tance from the core of the wheel. The function .of the consistency regulator is to control a supply of diluting water which is added to the incoming stream of stock so as to maintain automatically a substantially constant consistency in the stock entering the metering vat. In order to control the rate of inflow of diluted stock into the vat, the supply stream may be controlled by a suitable butterfly valve automatically movable in response to changes in the direction of variation of the level o fa float on the pool of t stock within the vat. The valve may be located at any convenient point, either in the supply stream of undiluted stock or in the stream of diluted stock' as it is about to enter the vat. According to the present invention mechanism is provided for handling large streams of pulp. This includes power means for o crating the valve, and automatic contro s for the power means responsive to changes in the direction of variation of level of the pool of stock in the vat. In general, where the opening of a ate or valve 1n a stream offluid is automatically varied in response to variations from a mean value of some characteristic of a portion of the fluid beyond the valve, such as the pressure or velocity of the fluid at a given point, or as in the present instance the surfacelevel of a pool, the mechanism for automatically controlling the valve usually causes the valve to move in a direction to oppose a change in pool level from the mean height. This corrective operation of the valve continues until the level returns to the mean height. if the pool rises, the control mechanism starts to close the valve and continues to close it not only after the poollevel has started to fall, but until the level has fallen back to the mean height. By that time the valve has been shut too far, and the level falls rapidly below the mean height, starting the control mechanism to move the valve toward its open position. Thus there is a tend ency on the part of the automatic controlling dis- Thus,

apparatus to fluctuate violently from one cxtreme to the other so that thepurpose of the apparatus is largely defeated. According to the present invention, this tendency to fluctuate or hunt is reduced to a slow drift between relativelynarrow limits by the use of a frictional'connection between a member movable directly in response to changes in the characteristic to be kept constant and control mechanism for adjustably moving the valve. In the present instance the directly movable membemmay be a float on the surface of the pool of pulp stock in the vat.

Rapid and efiicient mixing apparatus is i mixing tank, the agitating means being capable of forming rapid, turbulent currents in the stock in such a manner that there is up and downmixing as well as transverse mixing. .In this way the diluting water is quickly intermixed with the stock and the diluting effect of the water upon the consistency of the stock stream is quickly felt at the point of discharge from the mixing tank. This makes for lncreased sensitivity in the apparatus as a whole, which is an important and valuable feature. Further; to increase this sensitivity, the feeler element of the consistency regulator is preferably located close to the outlet of the mixing tank so that the lag between a change of the supply rate of the diluting water and its effect on the fceler is' reduced to a minimum.

For a more complete understanding of the invention reference may be had to the description thereof which follows and to the drawings of whicl.,- "Figure 1 illustrates diagrammatically apparatus embodying the invention.

Figures 2, 3 and 4 are similar views of modified forms of the invention.

Figure 5 shows diagrammatically hydraulic apparatus for controlling the stock level in the metering vat.

Figure 6 vshows on a larger scale a por- 'tion'of the mechanism shown in Figure 5.

Figure 7 shows a modified form of a portion of the invention. 's

Figure" 8 is a perspective view of a modified form of feeler for consistency regulator.

Referring in detail to Figure 1, 10- represents a supply tank for pulp stock coming l through a supply pipe 11 from a storage tank (not shown) or directly from a beater. Within the tank 10 are a suitable number of agitators 12 driven by a motor 13 to prevent settling of the fibers and also-to average up the consistency of the stock received through the pipe 11. The tank 10 is preferably of considerable capacity so that there is no abrupt fluctuation in the consistency of the stock taken therefrom. From a point near the bottom of the tank 10 a discharge pipe-14 runs to a centrifugal pump 15; A

second pipe 16 leads from a point about halfway up on the side of the tank 10 to the pump 15. The pipes 14 and 16 may be controlled respectively by suitable valves 17 and 18. Ordinarily stock is taken from the middle level of the tank 10 through the pipe 16, the pipe 14 being used when it is desired to empty the tank or in case' the level should temporarily falPbelow the orifice of the pipe 16. The pump 15 discharges into a pipe 20 which opens into the bottom of a suitable mixing tank 21. \Vithin the pipe '20 is a valve 22 preferably of the butterfly type which provides a variable supply port for the admission of liquid into the tank 21. The valve member itself may be in the form of an elliptical plate which fits diagonally across the cylindrical interior of the pipe when the valve is entirely closed and may be swung to a position in line with the axis of the pipe by a suitable lever 66 which may be operated by any convenient apparatus such as .an hydraulic piston contained in a cylinder 24. Within the mixing tank 21 suitable mixing apparatus may be provided. As shown, this may consists of a pair of marine propellers 25 mounted on a shaft 26 supported a short distance above .the bottom of the tank 21. This shaft may bc-connected to a suitable motor 27 for rotation. The blades of the propellers 25 are preferably of opposite pitch so that they throw streams in opposite directions against the sides of the tank. This causes a pair of circular currents rising at with diluting water at a point just prior to its entrance into the mixing tank. As soon i as the stock enters the mixing tank, the rapid mixing current-s carry it laterally and upwardly, the propellers churning the thick stock and the water together to form quickly an evenly diluted stock. If the rate of supply of water through the pipe 30 is increased or diminished, this change is almost immediately felt at the upper end of the mixing tank 21 by reason of the rapid circulation of the currents in the tank 21. The diluting water is'supplied through a suitable pipe 31 which is connected to a standpipe 32. From the latter a serigs of overflow pipes 33 lead after described in detail, so as to maintain a substantially constant consistency in the stock,

passing through the mixing tank 21.

At the upper end of the tank 21 a short "standpipe 35 projects upwardly into a metering vat 36 at one end ofwhich is a metering wheel 37. be similar to that described in my Patent No. 1,744,145, and may have a number of blades or paddles between which are the compartment-s successively filled by pulp from the. pool in the vat 36 as the metering wheel rotates. The pulp stock passing through the wheel is discharged-into a suitable pipe 38 through which it is-conducted to apparatus for further treatment. iVithin the vat 36 is a dam 40 to provide a spill-way in case of excessive high level of the pulp stock in the pool. Excess stock spilling over the crest of the .dam 40 may be conducted through a pipe 41 back to the supply tank 10. Ordinarily, however, the surface level of the stock pool in the vat 36 will be automatically maintained by the valve 22 below the crest of the dam 40 so that no diluted stock will be returned to the supply tank 10.

e For the control of the valve -22,'suitable mechanism may be provided including a float 42 in the pool of stock in the vat 36. This control mechanism may take various forms. For example, hydraulically operated control apparatus is illustrated in Figures 1 and 6. As shown, the float 42 maybe connected by a rod 43 to a lever arm 44 which may be pivoted as at 45. This arm carries a pair of spring-pressed friction members 46 and 47 adapted to press against opposite side surfaces of the vertical stem 50 of a slide valve 51. The pressure of the friction shoes 46 and '47 may be provided by a pairof springs 52 and 53, the force of which may be regulated by a pair of adjusting screws 54 and The stem 50 has a neutral or normal position relative to the arm 44. A pair of springs 56 The metering wheel 37 may and 57 connect the stein 50 with the arm 44 l in such a way as to tend to maintain thestem in its neutral position and to return the stem posed by the friction shoes 46 and 47. The

valve 51 may'slide'in a suitablecasing 60 and may be provided with suitable ports in a manner well known in the art by which a pressure fluid supply pipe maybe connected 5 with either one of two service pipes, the other service pipe being simultaneously connected with a discharge pipe. As shown, compressed liquidv or air may besupplied through a supply pipe 61, a discharge pipe 62 being also connected with the casing 60. A pair of service pipes 63 and 64 extend from the casing 60 to the hydraulic cylinder 24 so as to transmit fluid pressure to the chamber above orbelow a piston 65 in the cylinder 24 for the actuation of the valve 22. The piston 65 may be connected with the valve 22 by any suitable linkage such as a lever arm 66 as shown in Figure 1,.or a gear train as shown in Figure 5. are provided for the purpose-of steadying the operation of the va ve 22 and preventing the apparatus from hunting. This maintains the stock level in the vat 36 at a subdrift between predetermined maximum and minimum limits, which limits may be quite close together so there is little variation in the level of the pool.

The operation of the valvecontrol apparatus is as follows: Considering first, by way of comparison, what would happen if the stem 50 were pivoted directly to the arm 44 instead of frictionally connected through the shoes 46 and 47, it is evident that a rise or upward drift in the level of the pool would cause a rise in the float 42 and the stem 50. This would cause the valve 51 to admit pressure fluid into the service pipe 64 so as to move the valve 22 toward its closed position and thus to diminish or constrict the supply port for the incoming stream of stock. When the valve 22 had been closed sutliciently to stop the rise of the pool level, the valve 51 would still be open and would remain 45 open until the level of the pool dropped to normal. During the dropping of the pool level to normal, however, the valve 22 would still be closing so that by the time the valve 51 was closed to stop further closing motion 59 of the valve 22, the level of the pool would be'dropping rapidly owing to the excessive closing of the valve 22. This would carry the pool level below normal, resulting in the operation of the valve 51 to move the valve '22 toward its Wide open position. This opening motion would continue until the pool sur vface was back to normal level. Thus the levelof the pool would fluctuate violently through a wide range: Stabilization, how- Q ever, may be accomplished by the frictional I connection between the valve stem and the lever arm 44. If with-the arm and stem thus connected, the level of the pool should rise owing to an oversupply of incoming stock. the

float 42 would rise and would elevate the stem The friction shoes 46 and 47 stantially constant level, there being a slow 50 sufliciently to open the valve. 51 for the admission of pressure to the pipe 64. This would cause the piston'65 to move the valve 22 toward its closed position, constricting the supply port. The upward or downward movement of the stem.50 is stopped by engagement of the valve 51 with an end of the casing when the valve 51 is fully open. During the closing movement of the valve 22 the float 42 would continue to rise until the decrease in the supply stream of stock was sufiicient to stop such rise and to start a recession or downward drift ofthe level. During the rise of the float 42 the stem 50 is carried upwardly therewith until its motion is stopped by engagement of the valve 51 with the upper end of the casing 60. Further rising of the float '42 then results in a slipping of the friction shoes 46 and 47 on the sides of the stem 50 and an elongation of the spring 57. s As soon as the level of the pool starts its downward drift, the stem 50 is at once pulled downwardly by its frictional engagement by the arm 44 so that the valve 51 is closed and the further closing of the valve 22 is at once stopped. This maintains the supply Y port unchanged until the valve 22 is further actuated. Since the level of the pool is slightly dropping when the valve 51 is closed, it will ordinarily continue to drift downwardly, but at a slow rate. Meanwhile the tension of the spring 57 will tend to elevate the stem 50 to its normal position with respect tothe arm 44, this normal position having been disturbed by additional rise of the arm 44 after the stem had reached its upper limit. If the rate of descent of the pool level is very slow so that the upward motion of the stem 50 caused by the spring 57 is faster than the downward motion of they stem caused by the descent of the arm 44, the valve 51 may be again actuated to close the valve 22 a littlefurther, and hence to caus an additional constriction of the supply port. If, however, the descent of the pool level is at such a rate as to balance the rise of the stem 50 under the action of the spring 57, the pool level will return to its normal height by a gradual fall and at the same time the stem 50 will return to its normal position relative to the arm 44 without further change in the supply port. If the fall of the pool level should be at an excessive rate, i. e., more rapid than the elevation of the stem 50 by the spring 57, then the valve 51 is operatedto cause opening motion on the part of the valve 22 which would enlarge the supply port and tend to check the fall in the level of the pool even before it 11:) reached its normal position. A fall of the level of the pool below its normal height would result in similar operation of theapparatus but in the opposite direction. It is evident that with such apparatus, properly 12'.

ing wheel such as the wheel 37. In the oper-- aticn of this wheel the stock in the pool rushes into successive compartments so that there is asurging of stock in the pool which causes the float 42 to bob up and down constantly. This results in an oscillation of,

the stem up and down and a slight resulting oscillation of the valve 22 as the control valve 51 is alternately opened in opposite directions. A rise or fall in the average level of the pool, however, will resultin an elevation or depression of the average height of the stem 50 so that in the case of a rise, for example, the brief periods of pressure in the pipe 64 would be slightly longer than the periods of pressure in the pipe 63 and there would thus be a resultant movement of the valve 22 toward its closed position. This oscillating movement of the float 42 and of the parts connected therewith does not interfere with the effectiveness of the frictional connection between the stem 50 and the arm 44 which keeps the mean level of the pool limited to a slow drift within, a narrow range. The constant mo- -tion of the float 42 moreover assists the action of the shoes 46 and 47 and the

springs

56 and 57 since any tendency on the part of the shoes to stick against the sides of the v stem 50 is thus obviated. This mechanism which responds promptly to'changes of levelof the mean surface of the pool when it is at any level rather than at only normal level,

is particularly important where the .level is liable to be changed not only by the rate of supply of undiluted pulp from the tank 10 but also the rate of supply of diluting water from the pipe 30. It is obvious that if the consistency of the stock delivered from the Figure 1 a relatively small sampling pipe may be mounted within the supply pipe 35, this sampling pipe 70 leading from the outlet of the mixing tank 21 into a miniature vat 71 from which the stock may be metered by a metering wheel 72. The metering wheel 72 for the sampling stream is small compared with the metering wheel 37 for the vat. In the small wheel, pulp is'liable to wedge and stick in the angle between the paddles, thus changing the capacity of the wheel. To obviate such sticking, I may fill or block ofl", as at 69, the spaces between the paddles for a short distance from the core of the wheel. The vat 71 is set at such a height that the surface of the stock pool therein will have the same level as the stock spilling over the top of the pipe 35, that is, a substantially constant level. By rotating the metering wheel 72 at a constant rate, the rate of discharge of stock from the vat 71, and hence the rate of admission of stock thereinto, will be constant. Thus a constant velocity of flow may be maintained in the pipe 70. In this flow of constant velocity I may support a suitable feeler 73 in the shape of a ball as shown in Figure 1, or in any other convenient shape such as the horizontal "rod 730 shown in Figure 8. In order to obtain maximum sensitivity in the apparatus, the orifice of the sampling pipe 70 is located in the outlet of the mixing tank 21, and the feeler 73 is located as near as possible to the orifice so as ,to be in a position to react as soon as possible to a change in the consistency of the stock leaving the mixing tank. The feeler may be located a short distance above the orifice of the sampling pipe to avoid uncertainty of its operation arising from turbulence of the sampling stream at the orifice of the pipe. The feeler is mounted on a supporting stem 74 which may be attached to a lever arm 75 pivoted at one end as at 76. The stream of stock rising through the pipe 70 flows against the feeler 73 and pushes it upwardly against a suitable spring 80. The spring may be adjusted to balance any deslred thrust of the feeler 73 according to the stock consistency desired, by an adJusting screw 81. If the velocity of the stream in the pipe 70 is maintained constant by operating the metering wheel 72 at a constant rate, the upward pressure of the stream against the feeler 73 will vary as the consistency of the stock. If the stock becomes thicker; it will push more strongly on the feeler 73 and will swing the lever arm 75 upwardly, whereas a thinning of the stock in the pipe 70 will permit the arm 75 to swing 'below its normal position. Suitable mechanism may be provided to regulate the action of the valve 34 for the diluting water in accordance with the motions of the arm 75. For example, the valve 34 may be opened and closed by a reversible electric motor 82 controlled by a double throw switch connected with or including the free end of the arm 75. As shown, on the arm 75 is a contact member 83 which is adapted to contact with a point 84 when the arm swings up, and with a point 85 when the arm swings down. These points are connected with a source of electric energy and with the motor 82 in such a way as to cause the motor to run in a direction to shut the valve 34 when the contact member 83 touches the point 85, and to cause the motor to run in a direction to open the valve 34 when the member 83 touches the point 84. By locating the

points

84 and 85 close together the apparatus can be made to respond at once to very slight variations in the consistency of the diluted pulp. If, for example, the pulp supplied from the tank 10 thickens slightly in consistency, the additional push on the feeler 73 closes the

switch

83, 84 causing the motor to open the valve 34 wider to admit diluting water to the mixing tank 21 at an increased rate. The effect of this increase of diluting water is quickly felt in the pipe 70 owing to the rapid circulation and churning of the pulp and water within the mixing tank 21. As a result, the opening motion of the yalve 34 is quickly stopped when the consistency of the stock in the mixing tank 21 has been restored. to the desired value. The maintaining of a strictly constant velocity of flow in the pipe 70 is important in that it permits the use of the simple consistency regulating shown in Figure 1 in place of more elaborate apparatus which is necessary for successful operation in currents of varying velocity. A regulator of the latter type is illustrated in my Patent No. 1,744,145. r

In Figure 2 is illustrated a slightly modified apparatus, the chief difference being in the means for supplying undiluted pulp from the supply tank 10- to the mixing tank 21. Instead of an automatic valve 22 as shown in Figure 1, I may extend the supply pipe into a suitable tank 79 from which a pipe 86 leads into the bottom of the mixing tank 21. The diluting water 1s 1ntroduced into the pipe 86 through a pipe 87 which enters the pipe 86 at a point adjacent to the mixing tank 21. The flowof water through the pipe 87 may be controlled by a suitable valve 88 which is actuated by a consistency regulating apparatus responsive to a rotating paddle or feeler90, this type of consistency regulating apparatus being similar to that described in my Patent No. 1,744,145. A suitable dam 91 is provided in the compartment 79 to provide the spill- Way for excess stock which is pumped into the compartment 79. This excess is led back to the supply tank as through a suitable pipe 92. As the feeler 90 of the consistency regulating apparatus 89 is not appreciably affected in its operation by,moderate changes istead in 7;. sampling stream leading into a of flow in the stream in which it Works, it may be supported directly in the stream of stock entering the vat 36. v

As shown, however, it ,may be supported apparatus sampling vat 71 from which the stock is metered at a constant rate by the metering wheel 72,- this metered stock being conveniently discharged into the return ipe 92 which leads to the supply tank 10. he quantity of diluted stock returned to the tank 10 through the sampling meter 71 is not sufiicient to atfect the average consistency of stock in the tank 10 appreciably. This combination of a rotating feeler and a sampling stream may be used where an extraordinarily high degree of accuracy in the control of stock consistency is desired.

In Figure 3M1 electric apparatus for controlling the position ofthe valve 22 is illus' trated, the remainderof the apparatus therein shown being substantially identical with that illustrated in Figure 1. The valve 22 is located in the stock supply pipe 20 and is operable by a suitable electric motor 95 througha train of gears 96. For controlling the motor 95 a two-way switch may be employed, this switch including. a movable member 97 adapted to come into Contact with a pair of contact points 98 by upward motion or into contact with a pair of con-* tact points 99 by downward motion. The switch member 97 ma be carried on a' stem which may be frictionally connected with a lever 44 as hereinbefore described. The motor 95 is of any convenient reversible type, the field windings of the motor being connected respectively with the contact points 98 and 99 in such a manner as to operate the motor in one direction or the other according as the switch member 97 makes contact with either set of points. To

prevent accidental over=running of the motor which might result in damaging the valve apparatus, .1 may provide suitable limiting switches and 101. These switches normally close gaps in the circuits through the points 98 and 99 respectively. .If the valve 22 is moved to its fully opened position, a pin 102 engages the switch 101 and opens it, thus breaking the, circuit tending to operate the motor 95 in the direction to open the valve 22. In like manner, if the motor 95 moves the valve 22 to its fully closed position, the pin 103 is provided to engage the switch 100 and thus to stop the further action of the motor in this direction. 1, I

In Figure 4 the electrically operated mechanism for controlling the valve 22 is combined with an electrically operated consist .1:

ency regulating apparatus. This apparatus may include mechanism similar to that.described in my Patent No. 1,744,145, the control portion of the apparatus being contained in a suitable casing 110. Variations in the resistance offered by the stream of stock to the rotation of the feeler 90 cause electric contactsto be made for the operation of a ried too far. There will customarily follow through which water is supplied to the stream of stock entering the mixing tank 21. The operation of this apparatus is substantially the same as that of the apparatus illustrated in Figure 1.

A modified form of apparatus for controlling the valve 22 is shown in Figure 7. The lever arm 44 shown in most of the figures may be dispensed with, and the vertical rod 43, which is secured to the float 42, may extend through a pair of suitable guides and 121. A friction collar 122 is lightly clamped on the rod 43 between the

guides

120 and 121 as byadjustable springs 123. The collar 122 carries an arm 124 on which are mounted a pair of buntersl25 and 126 adapted to engage and rock respectively a pair of mercury switches 130and 131 of a well known type. 'Each of these switches is normally held open by a.v spring 132. The switches are adapted to be connected to an electric motor for operating thevalve -22 in lieu of the switches illustrated inFigures 3 and 4 for this purpose. In the operation of the apparatus, if the float causes the rod 43 to rise, the hunter rocks the switch to close it. This starts the motor 95 operating in a direction to close the valve 22. Theguide 120 may carry an adjustable stop 135 to stop the upward movement of thecollar 122 and arm 124 at the point where the bunter 125 opens the switch 130. If the rod 43 continues to rise, it slips through the collar 122 ,which is frictionally mounted thereon. Meanwhile the motor 95 is operating to reduce the incoming stream of stock and thus to lower the stock level in the vat 36. As soon as the level starts to falL-the collar 122 descends with the rod 43 and the switch 130 is thereupon opened by its spring 132, stopping the motor 95. This prevents the closing action of the valve 22 from being caraslow downward drift of level until the bunter 126 closes the switch 131 and starts the motor 95' operating to open the valve 22,

wider. As soon as the level starts to rise, the motor 95 is stopped. This prevents undesirably violent fluctuations of the level of the stock in the metering vat.

I claim:

1. Apparatus of the class described comprising a vat for pulp stock having an outlet port and an inlet port, means for controlling the outflow ofstock through said outlet port, and means for automatically maintaining a substantially constant consistency and volume rate of inflow of stock through said inlet port.'

2. Apparatus of the class described comprising a vat for pulp stock having an outlet port andan inlet port, means for controlling the outflow of stock through said outlet port,

means for automaticallycontrolling the volume flow of stock entering the vat through said inlet port, means for introducing diluting' water into the stock stream entering the vat prior to its passage through said inlet' rate, means for maintaining a flow of stock into said vatth'rouga said inlet port, means for automatically controlling at a point spaced from said inlet port the volume flow of said stream in accordance with the volume of stock in the vat, means for admitting diluting water to said stream of stock at a point between the point ofcontrol of said stream of stock and said inlet port, and means responsive to the consistency of the stock passing through said inlet port for automatically controlling the volume flow of said stream of diluting water. I

4. Apparatus of the class described comprising a pulp stock vat having an inlet port and an outlet port, means for causing a substantially constant flow of stoclnfrom said vat through said outlet port,automatic means for maintaining an inflow of stock through said inlet port substantially equal to said outflow, and means for automatically maintain ing a substantially uniform consistency in said inflowing stock, said-last named means lncluding means for lnt-roducing diluting water into said inflowing pulp stream prior to its passage through said inlet port, means' for automatically controlling the supply of said diluting water in accordance with the consistency of the pulp passing through said inlet port, and means for thoroughly. mixing said diluting water into the pulp stock stream prior to its passage through said inlet port.

.5..Apparatus of the class described comprising. a vat for pulp stock having an inlet for the inflow of stock, a conduit for the stream of pulp stock inflowing into the tank, a water pipe discharging intosaid conduit to dilute the stock stream, a consistency regulator responsive to the consistency of the stock entering the vat for controlling the flow of diluting water into said'conduit to maintain the consistency of the entering stock substantially constant, a valve in said c'on-' duit at aQpoint upstream relatively to the water pipe connection,'and means for regulating said valve automatically in response to the quantity of stock in said-vat;

6. Apparatus of the. class'described 'comprising a vat for pulp stock having an inlet for the inflow of stock into the vat, means for leading off a-sampling'str'eam of substantially constantvelocity from the inflowing stream of stock, means for automatically A predetermined rate.

regulating the consistency of the stock in said inflowing stream, said regulating means including a feeler immersed in said sampling stream, and means for metering stock from I said vat at a predetermined rate.

7. Apparatus of the class described comprising a vat for pulp stock having an inlet for the inflow of stock into the vat, means for leading oil a sampling stream of stock 3 "from the stream entering the vat, means for automatically regulating the consistency of the stock in said inflowing stream, said-regulating means including a feeler immersed in said sampling stream, mechanism for main- 5 taining theflow of said sampling stream at box for rapidly and continuously mixing the contents thereof, means for supplying a stream of stock to said box, means for supplying water to said box to dilute the stock supplied thereto, means responsive to changes in consistency'of stock leaving the box for automatically regulating the water supply to,

maintain the stock passing from the box to the vat at-a substantially constant consistency,

and means responsive to changes in the level of stock in the vat for automatically regulating the rate of delivery of stock to the vat. 9. Apparatus of the class described comprising a vatfor pulp stock, means for metering stock from said vat at a constant volume v rate, means for supplying a stream of stock to said vat including a mixing box adjacent to said vat, means for supplying diluting water to said box, means in said box for mixing thoroughly the supplied stock and diluting water and for circulating the mixture rapidly in the box, means for automatically regulating the rate of flow of stock entering the box and vat to maintain the quantity of stock therein substantially constant, andmeans for regulating the supply of diluting water to maintain the consistency of the stock flowing into the vat substantially constant, said water regulating means including means for leading off a sampling stream of diluted stock from said box at a constant velocity, and a feeler supported in said sampling stream.

10. Apparatus of theclass described comprising a consistency'regulator having a feeler to be supported in a stream of stock, and

means for maintaining a constant velocity of 1 flow in the portion of the stream contiguous to said feeler.

11. Apparatus for regulating the consistency of a delivery stream of pulp stock, which includes means for leading off from said-delivery stream a sampling stream of stock, a

feeler in said sampling stream, means for positively feeding said sampling stream at aconstant volume rate of flow, and mechanism responsive to the resistance of said feeler to I the flow of the stock in said sampling stream for altering the consistency of the stock in said delivery stream.

12. In combination with apparatus forleading oil a sampling stream of pulp stock to test and regulate the consistency thereof, means for positively feeding said sampling stream at a constant volumerate of flow, said means comprising a metering device, and means for driving said device at a constant rate.

13. Apparatus for maintaining substantially constant a characteristic of a portion ofa stream of fluid depending on the rate an element having a limited range of movement and movable in said range by frictional engagement with said member.

14. Apparatus for controlling a supply streamof fluid in respdnse to changes in a characteristic of a portion of the fluid which has passed the point of supply control, said apparatus including a valve. in said supply stream, reversible ower means for moving said valve toward its open and closed posi-- tions, a control element movable from an intermediate position to positively limited positions in which respectively said power means are operated to move said valve in corresponding directions, a member positively movable in response to changes in said characteristic, said member having frictional engagement with said element so as to move-said element to one or the other of its limiting positions, and spring means between said member and element tending to maintain said member and element in a predetermined relation to each other.

15. Apparatus for maintaining a pool of liquid at 'a substantially constant level during a continuous inflow and outflow of liquid into and out of said pool, said apparatus comprising a valve in the incoming stream, rover sible power means for moving said valve toward its open and closed positions, and means responsive to changes in level of said pool for controlling said power means, said power controlling means including a float on said pool, a member positively movable by the rise and fall of said float, and an element frictionally engaged by said member and movable thereby between limiting positions in which respectively said element causes the. actuation of said power means to move said-valve correspondingly.

16. Apparatus for maintaining a pool of liquid at a substantially constant level during a continuous inflow and outflow of liquid into and out of said pool, said apparatus comprising a valve movable to regulate the rate of said inflow of liquid, reversible power means for moving said valve toward its open and closed positions, a float on said pool, a member movable positively by rise and fall of said float on said pool, and a control element movable by frictional engagement with said mem her in a narrow range between limiting positions, said control element having a normal intermediate position from which it is movable by a rise of the float to cause said power means to move said valve toward its closed position, said element being movable by a fall of said float to the opposite limiting position to cause said power means to-movesaid valve toward its open position.

17. Apparatus of theclass described comprising a vat for pulp stock having an inlet for the inflow of stock into said vat, a valve for regulating the inflowing stream, a float in said vat, valve-actuating means, and control connections between said float and said actuating means, said connections including an element having a'norrowly limited range of motion and a second element positively movable by said float and in frictional en gagement with said limited element.

18. A metering wheel of small size for a sampling stream of pulp stock, comprising an axis, a plurality of paddles projecting outwardly from said axis, the spaces between successive paddles being blocked off for a short distance from said axis.

19. A method of maintaining near a predetermined height the surface level of a pool having an inflow and outflow of liquid, and of minimizing the rate of variation of said level, which comprises varying the rate of inflow independently of the quantity of liquid present in the pool at any moment to oppose variation of surface level, and automatically controlling the variation of inflow in response to changes in direction of variation of level.

20. A method of maintaining substantially constant the quantity of a fluid in abody thereof having a supply stream adding fluid thereto and a discharge stream taking fluid therefrom, which comprises constricting or amplifying one of said streams independently of the quantity of fluid actually in said body at any moment, and controlling said constricting or amplifying action in response to changes in direction of variation of said quantity.

21. A method of maintaining substantially constant the level of a pool of liquid in a vessel to which liquid is being added through a supply port and from which liquid is being discharged, which comprises constricting the supply port in response to an upward drift of said level from normal until a downward drift sets in, maintaining said supply port unchanged during the downward drift to normal level unless the rate of said downward drift is excessive or deficient, and enlarging said port in response to excessive rate of downward drift or additionally constricting said port in response to deficient rate of downward drift toward normal, said method also comprising enlarging said supply port in response to a downward drift of level from normal until an upward drift sets in, maintaining said supply port unchanged during said upward drift to normal level unless the rate of said upward drift is excessive or deficient, and constricting said port in response to excessive rate of upward drift or additionally enlarging said port in response to deficient rate of upward drift toward normal level;

22. A method of delivering pulp stock at a substantialy constant tonnage rate, which comprises maintaining a pool of stock, metering stock from said pool at a constant volume rate, providing a supply stream of stock for said pool, diluting the stock in the supply stream to the consistency desired, and admitt'ing diluted stock to the pool at a rate substantialy the same as the rate of discharge of the stock from the pool.

23. A method of delivering pulp stock at a substantially constant tonnage rate, which comprises maintaining a pool of stock, me-

tering stock from said pool at a constant volume rate, providing a supply stream of stock, introducing diluting water into said stream, mixing said water thoroughly with the stock in said stream immediately prior to its entrance into said pool, regulating the rate of supply of diluting water to maintain the consistency of the mixed dilutedstock substantially constant, and controlling the stock supply stream to maintain a volume rate of admission of diluted stock into said pool substantially equal to the rate at which the stock is metered from the pool.

24. A method of delivering pulp stock at a substantially constant tonnage rate, which comprises maintaining a pool of stock, metering stock from said pool at a constant volume rate, providing a supply stream of stock, introducing diluting water into said stream, mixing said water thoroughly with the stock in the stream, regulating the rate of addition of Water to. maintain the consistency of the mixed diluted stock substantially constant, admitting the diluted stock to the pool, and regulating the flow of the supply stream of undiluted stock so that its flow added to that of the diluting water substantiallyequals the discharge flow from the pool.

In testimony. whereof I have aflixed my signature.

MILTON O. SCHUR.