US2870690A - Head box for paper making machines - Google Patents

Description

Jan. 27, 1959 W. S. CORBIN ET AL HEAD BOX FOR PAPER MAKING MACHINES Filed NOV. 6, 1952 3 Sheets-Sheet 1 IN VEN TOR.S

M/cs/ey 5 Cor/in Henr/K W1 Iden r/es lq arson A orney.

Jan. 27, 1959 w. s. CORBIN ET AL 2,870,690

HEAD BOX FOR PAPER MAKING MACHINES 3 Sheets-Sheet 2 Filed Nov. 6, 1952 M m m M DIZIK /es W Walks; BY A223 ol r; ep

Jan. 27, 1959 w. s. CORBIN ET AL 2,370,690

HEAD BOX FOR PAPER MAKING MACHINES 3 Sheets-Sheet 3 Filed Nov. 6, 1952 J1 Is-. E

INVENTORS 5. Corbin United States Patent F HEAD BOX FOR. PAPER MAKING MACHINES Wesley S. Corbin, Charles M. Pearson, and Henrik Walden, Watertown, N. Y., assignors, by mesne assignments, to The Black-Clawson Company, Hamilton, Ohio, a corporation of Ohio Application November 6, 1952, Serial No. 319,157

11 Claims. (Cl. 92-44) This invention relates to head boxes for Fourdrinier paper making machines.

The invention has as an object a head box embodying a construction such that the box will perform efiiciently over a wide range of weights of paper and speeds of paper on the machine. For example, this head box will operate efficiently over a range of speeds of 125 feet to 1000 feet per minute and on a basic weight range of from 25 lbs. to 125 lbs., and with a stock consistency. range varying from .3% to .7% fiber.

This performance is obtained by keeping the flow of stock through the successive passages of the box under what might be termed controlled agitation up to the time the stock is discharged through the slice lip, the invention embodying a structural arrangement by which the box can be adjusted for such controlled agitation of the stock for different consistencies of stock moving at different velocities.

The invention :has as a further object the provision of means for the removal of air from the stock so when the stock is discharged through the slice, it is practically free from entrapped air.

The invention has as a further object a head box embodying a structural arrangement which minimizes the collection of slime and fiocs of fiber. I

The invention consists in the novel features and in the combinations and constructions hereinafter set forth and claimed.

In describing this invention, reference is had to the accompanying drawings in which like characters designate corresponding parts in all the views.

In the drawings Figure 1 is a side elevational view of a head box embodying our invention.

Figure 2 is a front elevational view of the head box with parts broken away and parts in section.

Figure 3 is a vertical sectional view taken on line 3-3, Figure 2.

Figure 4 is an enlarged fragmentary sectional view taken on line 4-4, Figure 3.

The head box comprises a heavy casting or structural base member mounted upon asuitable concrete foundation 10. This base member is formed with an upper concave wall 11 which merges with a downwardly extending portion 12 to form a permanent ridge 12' extending across the full width of the head box. The forward end of the curved surface 11 joins a horizontal forwardly extending portion 13 which is supported by a vertically extending forward wall portion 14 and forms a portion of the lower slice lip.

The box proper is formed with side plates 15 resting at their lower edges on the concrete foundation 10 and being attached to the ends of the base member. The lower portions of the side plates 15 are formed with forwardly extending portions 16. The bottom wall 17 of the box is positioned upon the concave surface 11 of the base member following the contour thereof and extending downwardly, as at 18, over the surface of the rear wall 2,870,690 Patented Jan. 27,1959

12 of the base, and being fixedly secured, as by welding, to one edge of an inlet slot 20 formed in a tubular member 21' extending transversely of the head box and suitably supported, as by a concrete foundation 22.

The rear wall 24 of the box is attached to its lower edge to the opposite edge of the slot 20.. The lower portion 25 of the rear wall and the lower portion 27 of the depending bottom wall diverge outwardly and upwardly from the slot 20 and form the lower portion of an up-flow compartment, the upper portion of which is formed by a partition member designated generally 28 and consisting of plates 29, 30, 31, 32, 33, 34, extending transversely of the box. The lowermost plate 29 is positioned slightly above the ridge 12' or crest of the bottom wall'of'the box to provide a slot 36 through which a portion of the stock flow passes forwardly into the lower endof the down-flow compartment which is formed by the partition 28 and the front wall 37 of the box. The uppermost plate 34 has its upper edge formed as shown in Fig. 3 with a convexly curved face 38 on its forward side to provide for smooth flow of stock thereover with minimum tendency to cavitation and undesirable fiber or slime deposits such as may result from a flowv of stockover a vertical surface. g p

The tubular inlet member 21 forms a stock inlet chamber 39 which is connected to the stock supply through a plurality of rearwardly extending flanged pipe members 40. The chamber 39 forms in effect anexplosion chamber, since the stock flowing through the inlet pipes 40v travels at relatively high velocity and, due to the large cross sectional area of the member 21, the stock is permitted to expand suddenly, so to speak, whereby the velocity is reduced and a high static head is formed, creatin the first turbulence, or agitation, of the stock. f. The up-flow of stock through the inlet slot 20 is restricted by a baffle 42 extending transversely of the box between the inclined side walls 25, 27, and this bafile is of inverted teardrop shape including side portions 44 converging upwardly to an apex 45. This baffie is adjustable vertically toward and from the inlet slot 20. Because of the restriction by baffle 42 of the flow area between itself and the sides 25, 27, the velocity of the stock is again increased, but as it flows upwardly into the broader portion of the up-flow compartment, the velocity is decreased. The inverted teardrop arrangement of battle 42 promotes smooth deceleration of this upward flow of stock with minimum tendency to cavitation.

To the inner surface of each end wall 15 of the box, there are fixedly secured, as by welding, a plurality of pairs of angle strips 48, see Figure 4, these strips extend-v ing vertically in parallel spaced relation and providing a T-slot in which there may be mounted spacing blocks 50. 1

This T-slot arrangement is to provide a mounting for baffles 51 in the up-flow and down-flow compartments.

In cross sectional form, the baffles51 are of tear-drop bafiles, and to each end plate there is secured,"as by screws 57, a block 58 slidably mounted between the guide rails 48 for cooperation with spacing blocks 50 of the proper selected heights to support the baflies 51 in the desired positions.

respective The baffle 42 controlling the inlet slot 20 is constructed with a shaft 60 extending therethrough and outwardly through vertically arranged slots 61 in the end plates of rack 72 having a threaded stem 73 extending through I a bracket 75 carried by the plate. 67, the stem being prov ded with adjusting nuts- 76 above and below the bracket and by adjusting the nuts 76, the rack is moved vertically.

The bafile 42 is fixedly secured at each end to a sleeve encircling the shaft, the sleeves being also fixedly secured to the bearing members 64 as by set screws, see Figure 2. With this arrangement the baffle is adjusted vertically at one side of the machine toward and from the inlet slot and is restrained against rotation during such adjustment.

It is well known that every furnish or stock solution has its flocculating time. This means that if the fibers in the stock remain in the same relative condition, either because of stagnation, or uniform velocity, for a certain period of time, the fibers will tend to become attached to eaehother and form clots or fiocs. There is a standard. procedure used in determining the time required to cause this so-called' flocculation of the fibers, and this flocculation time is standard for any given furnish. If at any time within theflocculating period, the fi bers are violently agitated, or disturbed, 'the tendency to flocculation isbroken up. This flocculation of fibers is aserious problemin manufacturing paper on a Fourdrinier machine. If the fibers are discharged through the slice onto the forming wire in flocs or clots, the qualit-y of the sheet will be impaired, the non-uniform distribution of the fibers adversely affecting the quality of the-paper from a utility standpoint.

The baflles 42, 51 are eflfective to reduceflocculation ofthe stock to a minimum and if the baflies are properly spaced apart, flocculation can be entirely eliminated. As the flow of stock encounters each baflle, its progress is restricted in moving through the reduced area between the baflle and the sides of the up-fiow and down-flow compartments. This restriction causes an increase in the velocity of the movement of the stock, but after the stock has passed the baffle, its velocity is reduced. This periodic change in the velocity of the stock creates considerable agitation of the stock and, as previously pointed out, this avoids flocculation of the fibers. The baflies 51 are spaced apart proper distances in accordance with the determined flocculation time of the stock. This-adjustment is by the employment of the spacer blocks 50 positioned in the guide pieces 48. The bafiles, because of their structural arrangement, also serve an additional purpose.

Another problem in the manufacture of paper is caused by air entrapped and absorbed in the stock. The baffles of teardrop shape tend to collect small bubbles of air from the stock and to discharge them off the points or apexes 54. These bubbles rise rapidly in the up-flow compartment and collect on the surface of the pond where they are eliminated.

Such air as remains in the stock during its downward flow, in the down-flow compartment, tends to collect on and to follow down the. forward wall 37 of the box, and thebubbles passing off of the apexes 54 of the baffles 51 likewise move toward the; wall 37.

The bottom wall of the box inclines downwardly, as

at 80, from the ridge 12' and the front wall of the up.- flow compartment, and. forms the. bottom wall of a discharge compartment or passage 81 which curvesupwardly and communicates with the slice opening 82. The top wall 83 of the discharge compartment 81 likewise curves upwardly and at the joinder of this wall with the front wall 37, there is provided a slot 84 communicating with a compartment 85 provided at one or both ends with a suction outlet pipe 86. The slot 84- is in the nature of an air vent for removing the accumulation of air bubbles traveling down the surface of the front wall 37, and it will also be seen in Fig. 3 that since the slot 34 is located at a position well below the ridge 12' where the wall 83 is formed to introduce a considerable restriction of the flow area of the compartment or passagev 81, the resulting change of the pressure head to velocity promotes the release of entrained'air bubbles at the top of this passage for removal by way of the slot 84.

There is journalled in the box and extending transversely in the discharge compartment 81, a distributor roll 88, the top and bottom walls of this passage diverging upwardly from the vicinity of the slot 84 to enlarge the passage sufiiciently for reception of the distributor roll 88. This roll is mounted upon a shaft 8% journalled in bearings mounted on the portions 16 of the side plates 15 of the box. One end of the shaft, as 91, extends outwardly through the bearing for the reception ofa pulley or gear to effect rotation of the roll. The roll consists of a series. of disks 93 arranged in spaced apart relation on the shaft with a plurality of rods 94 extending parallel with the shaft 89 through the disks 93 adjacent the periphery thereof, as shown in detail in the copending application of W. S. Corbin, Serial No. 238,723, filed July 26, 1951, and assigned to the same assignee as this application. The function of this roll is to eflect agitation of the stock without imparting movement thereof transversely of the box.

The top wall 83 of the discharge compartment 31 extends upwardly about a portion of the distributor roll 88, the roll being of such diameter that its periphery moves in close adjacency to the bottom and top Walls of the compartment, whereby the roll is continually and completely submerged in the stock flowing through the discharge compartment. 81.

The forward lower portions 16 of the end walls 15 are provided at their upper edges with laterally extending plates reinforced by brackets. 101. There is slidably mounted on the plates 100, a deck having end walls 102, a bottom wall 103, and a top wall 104. The end walls 102 engage the inner surface of the wall portion 16 of the box and carry laterally extending members 106 min forced with angle pieces 107, the members 106 being slidably mounted upon the plates 100.

The deck structure is formed with a plurality of vertically extending walls or partitions 108, and a rear wall 109 to which bearing blocks 110 are mounted and in which there is journalled a shaft 111 provided at one end with a hand wheel 112. The shaft 111 carries a pair of wormv gears 113 arranged in mesh with worm wheels 114 forming nuts for screws 115 having eye heads attached to the forward Wall of the box, as by a rod 116. With this. arrangement, rotation of the hand wheel 112 effects forward and rearward movement of the deck structure. The bottomwall 103 extends forwardly and upwardly from the roll 88 to the slice 82 forming a continuation ofthetop wall of the discharge compartment. An upper slice lip is hingedly secured to the front end of the bottom wall 103, and mechanism is provided for adjusting thisupper lip 12 0 toward and from the bottom lip of the slice 82. There is mounted on the top wall. 104 of. the deck structure, a plurality of gear housings 12-2 in which there is journalled a shaft 123 extending horizontally and also supported in bearings 124 and. provided. on at least one end with a hand wheel 125.; The shaft has fixed on it worms engaging with worm wheels 128. which constitute nuts for screws 129 extending. vertically and being secured at their lower ends in housings 130. mounted for vertical sliding movement on a front wall 131 of the deck structures A beam in the form of a tubular member 132 is carried by the housings; 130 and extends transversely across the front of the deck. A series of relatively closely placed screws 135 are attached to the forward edge of the lip 120 and extending through the beam 132, these screws being provided with upper and lower nuts, 136 to effect individual vertical adjustment of the screws to level the lipv 120, initial vertical adjustment of the lip being effected by rotation of the hand wheel 125.

As clearly shown in Fig.3, the ridge 12 is located in substantially the same horizontal plane with the forming wire 140 where the latter leaves the-breast roll 141.; The entire approach flow of stock to-the' wire through the discharge passage 81 is therefore below the .wire level except for the short distance after leaving the distributor roll 88 to the slice. It is accordingly apparent thatfsince some head of stock is required above the ridge-12', which even for minimum speeds will extend above the ridge to a level appreciably higher than the upper; slice lip 120, this construction assures both that the, distributor roll 88 beat all times completely submergedin stock, andalso that no part of this discharge passage will be above the liquid level during operation, thus preventing possible drying and tendency to collect fiber thereon.

In addition, with the top Wall portion 103 of the discharge passage inclined upwardly from the distributor roll 88 to its junction with the upper slice lip 120 as shown, if air bubbles should travel with the stock beyond the slot 84, they will tend to migrate upwardly and outwardly along the wall 103 until they are entrained by the scouring action of the stock as discharged there by the slice. This discharge passage construction therefore provides for control of the flow distribution ofythe stock at a position close to the slice even at minimum speeds of operation, and at the same time it gives maximum assurance against possible depositing of air, slime or the like tending to build up obstructions to smooth sheet formation as Well as to the formation of lumps capable of subsequently breaking off into the fiow'and forming defects in the sheet.

What we claim is: i t

' l. A head box for a Fourdrinier paper machinehaving a forming wire and a breast roll supporting the wire in a predetermined horizontal plane, comprising front and rear-walls and a pair of side walls defining a main chamber for receiving the paper making stock', said chamber being open to atmospheric pressure at the top thereof, means including a bottom wall forming a ridge extending permanently across said main chamber and defining therewith a rear and a front compartment, means for delivering stock into said rear compartment for flow therefrom over said ridge to said front compartment, means forming a slice in substantially the same horizontal' plane as the wire for delivering the stock from said front compartment to the wire, means including a top wall forming a discharge passage leading from said front compartmentto said slice, means establishing said ridge at substantially the same horizontal level as the wire to provide for slow speed operation of said head box with a correspondingly low pressure head of stock abovesaid ridge, removable partition means above said ridge 'for raising the height of said front compartment to increase the pressure head ofstock therein for correspondingly increasing speeds of operation, a distributor roll journaled within said discharge passage for agitating the stock flow through said passage to even the flow distribution of the stock 'therethrough, said top wall having a substantial portion of the length thereof located below the horizontal level of said ridge and the remainder thereof located not substantially higher than said ridge to maintain said distributor roll submerged in'stock through the full speed range of operation of said head box, means forming a bleed chamber in said head box located forwardly of said ridge, said top and said bottom walls including portions located between said ridge and said distributor rollin relatively close proximity to each other to introduce a restriction in said discharge passage inter mediate said ridge and said distributor rolls with resulting change of the pressure head on the stock flowing therethrough to velocity promoting release .of entrained air bubbles at the top of said restriction, means defining a slot in said top wall extending substantially the fulldefining therewith a rear and a front compartment, means including partition members removably mounted above said ridge for extending the heights of said compartments in accordance with the desired pressure head of stock in said chamber, means for delivering stock into the lower; end of said rear compartment for flow upwardly therein andover said partition means to said front compartment, means forming a slice in substantially the same hori-. zontal plane as the wire for delivering the stock from said front compartment to the wire, at least one imperf'oratebafile member extending between said side' walls in each of said compartments, said baffle members. beingof' generally teardrop configuration in cross section providing a rounded surface on one side thereof tapering to an apex on the opposite side thereof, and means mounting said baffle members with the apex of each thereof pointing-in the direction'of stock flow therepast to cause sudden acceleration of said stock flow'followed by more gradual deceleration and thus to effect agitation of said stock with minimum turbulence andtendency to. flocculation of the fibers therein. a I I 3. A head box for a Fourdrinier paper machine having. a formingwire and a breast roll supporting the'wire'in a predetermined horizontal plane, comprising front and rear. walls and a pair of side walls defining. a main chamber for receiving the paper making .stock, said chamber being open to atmospheric pressure at'the top. thereof, means including a bottom wall forming a ridge, extending permanently across said main chamber and defining therewith a rear and a front compartment, means including partition members removably mounted above said ridge for extending the heights of said compartments in accordance with the desired pressure head of stock in said chamber, means for delivering stock into thelower end of said rear compartment for flow upwardly therein and over said partition means to said front com partment, means forming a slice in'gsubstantially the same horizontal plane as the wire for delivering the stock from said front compartment to the wire, at least one imperforate baffle member extending between said side walls in each of said compartments, said .baffle members being of generally teardrop configuration in cross section providing a. rounded surface on one side thereof tapering to an apex on the opposite side thereof,

means mounting said baffle members with the apex of each thereof pointing in the direction of stock flow-therepast to cause sudden acceleration of said stock flow followed by more gradual deceleration and thus to effect agitation of said stock with minimum turbulence-and tendency to flocculation of the fibers therein, and the uppermost of said partition members having a convex surface on the side thereof facing said front compartment to minimize cavitation in the flow of stock over asro geao *2 wire in a predetermined horizontal plane, comprising frontand rear walls and a pair of side walls defining a main chamber for receiving the paper making stock, said chamber being open to atmospheric pressure at the top thereof, means including a bottom wall forming a ridge extending permanently across said main chamber and defining therewith a rear and a front compartment, meansincluding partition members removably mounted above said ridge for extending the heights of said coinpartments in accordance with the desired pressure head of stock in said chamber, means for delivering stock into the lower end of said rear compartment for flow upwardly: therein and over said partition means to said front compartment, means forming a slice in substantially the samehorizontal plane as the wire for delivering the stock from said front compartment to the wire, means including atop wall forminga discharge passage leading from said front compartment to said slice, means establishing said ridge at substantially the same horizontal level as the wire toprovide for slow speed operation of said head boxwith a correspondingly low pressure head of stock above said ridge, a distributor roll journaled within said discharge passage for agitating the stock fiow through said passage to even the fiow distribution of the stock therethrough, said top wall having a substantial portion of the length thereof located below the hori zontal level of said ridge and the remainder thereof located notsubstantially higher than said ridge to maintain said distributor roll submerged in stock through the full speed range of operation of said head box, and at least-oneimperforatebafl'le member extending between said side walls in each of said compartments, said baffle members being of generally teardrop configuration in cross section providing a rounded surface on one side thereof tapering to: an apex on the opposite side thereof, and; means mounting said baffle members with the apex of each thereof pointing in the direction of stock flow therepast to cause sudden acceleration of said stock flow followed by more gradual deceleration and thus to effect agitation of said stock with minimum turbulence and tendency to flocculation of the fibers therein.

5; A head box for a Fourdrinier paper machine comprising front and rear walls and a pair of side walls delining a main chamber for receiving the paper making stock, partition means dividing said chamber into front and rear compartments, means for delivering stock into the-lower end of said rear compartment for flow up wardly therein and over said partition means to said front compartment, means forming a slice atv the lower end of said compartment for discharge of the stock therefrom, at least one irnperforate baffle member extending between. said side walls in each of said compartments, said baflle members being of generally tear-drop configuration incross section providing a rounded surface on one side thereof tapering to an apex. on the opposite side thereof, means mounting said bafile members extending horizontally across said compartments intermediate said partitlOD. means and the adjacent one of said front and rear walls with the apex of each thereof extending in the direction of the stock flow therepast through the associated said compartment, and each said baffle being of a width measured from back to front of the associated compartment less than the corresponding dimension of said compartment to cause abrupt narrowing of the flow passage through said compartments for sudden acceleration of the flow of. stock past both sides thereof followed by progressivejwidening of such flow passage for controlled deceleration: of. said. stock. with minimum turbulence.

. 6. A head box for a Fourdrinier paper machine comprising. front and rear walls and a pair of side walls delining; a; mainchamber for receiving the paper making stock, a.- partition dividing said chamber into front and rear: compartments and including removable partition membersfor varying the effective height of said partition, means: fon delivering stock into-the lower end of said rearcompartment for flow upwardly net-em and oversaid. partition means to said frontcompartment, means forminga slice at the lower-end of said compartment for discharge of the stock therefrom, at least one imperforatebaffle member extending between said side Walls in each of said compartments, said baftle members being'of gen-- erally tear-drop configuration in cross section providing a rounded surface on one side thereof tapering to an apex on the opposite side thereof, means mounting said baflle members extending horizontally across said compartments intermediate said partition means and the adjacent one of said front and rear walls with the apex of each thereof extending in the direction of the stock flow therepast through the associated said compartment, eachsaid baffle being of a width measured from back to frontof the associated compartment less than the corresponding dimension of said compartment to-cause abrupt narrowing of the'fiowpassage through said compartments for sudden accelerationof the flow of stock past both. sides thereof followed by progressive widening of such flow passage for controlled deceleration of said stock with. minimum turbulence, and means forming vertically adjustable mountings for said bafile members to provide forvarying the positions of said bafile members in accordance with the height of said partition. I

' 7. A head box for a Fourdrinier paper machine having a forming wire auda breast roll supporting the wire in a wire, means including a top wall forming a discharge passage leading. from said front compartment tosaid slice; means establishing saidv ridge at substantially the same. horizontal level as the wire to provide for slow speed operation of said head box with a correspondingly low pressure head of stock above said ridge, removable partition means above said ridgefor raising the height of. said front compartment to increase the pressure head of- 3 stock therein for correspondingly increased speeds of operation, said bottom wall extending. downwardly and forwardly from said ridge toward said front wall and cooperating. therewith and with said top wall to establish.

a constriction. in said discharge passage intermediatesa'id. ridge and said slice, said top and bottom walls having: relatively divergingportions between said constriction and:

said slice to enlarge the portion of said discharge passage defined thereby, a distributor roll journaled' Within. saidenlarged portion of saidldischarge passage, and said top: wall having a substantial portion of: the length; thereof-1 located below the horizontal level of said ridge and theremainder thereof located not: substantially higher than said ridge to maintain said distributor. roll submerged in; stock through the full speed range of operation of said head'box.

'8. A. head box for a Fourdrinier paper machine having a forming wire. and? a breast. roll supporting the wire' in:

a predetermined horizontal plane,- comprising, front and 65 her for receiving the paper making stock, meansinclud-= rear walls and a pair of side walls defining a main chanting a bottom wall'forrning a ridge extending permanently across said main chamber and defining therewith a rear and a front compartment, means for delivering stoclciuto: said rear compartment for flow therefrom over said ridge to said front compartment, lips forming a. slice ou.t-'

. let in substantially the. same horizontal plane as thewiro for delivering'the stock. from said front compartment to the wire,.means including a. top wall. forming at discharge passage leading from. said front compartment to -said slice outlet, means establishing said ridge at substantially the same horizontal level as the wire to provide for slow speed operation of said head box with a correspondingly low pressure head of stock above said ridge, removable partition means above said ridge for raising the height of said front compartment to increase the pressure head of stock therein for correspondingly increased speeds of operation, said bottom wall extending downwardly and forwardly from said ridge toward said front wall and cooperating therewith and with said top wall to establish a constriction in said discharge passage intermediate said ridge and said slice, said top and bottom walls having relatively diverging portions between said constriction and said slice to enlarge the portion of said discharge passage defined thereby, a distributor roll journaled within said enlarged portion of discharge passage, said top wall having substantially the entire portion of the length thereof upstream of said distributor roll located below the horizontal level of said ridge to maintain said roll submerged in stock through the full speed range of operation of said head box, and said top wall being inclined upwardly and forwardly from said distributor roll to said slice outlet to promote discharge of entrained air bubbles with the stock flow through said slice outlet.

9. A head box for a Fourdrinier paper machine having a forming wire and a breast roll supporting the wire in a predetermined horizontal plane, comprising front and rear walls and a pair of side walls defining a main chamber for receiving the paper making stock, means including a bottom wall forming a ridge extending permanently across said main chamber anddefining therewith a rear and a front compartment, means for delivering stock into said rear compartment for flow therefrom over said ridge to said front compartment, means forming a slice in substantially the same horizontal plane as the wire for delivering the stock from said front compartment to the wire, means including a top wall forming a discharge passage leading from said front compartment to said slice, means establishing said ridge at substantially the same horizontal level as the wire to provide for slow speed operation of said head box with a correspondingly low pressure head of stock above said ridge, said bottom wall extending downwardly and forwardly from said ridge toward said front wall and cooperating therewith and with said top wall to establish a constriction in said discharge passage intermediate said ridge and said slice, said top wall having a substantial portion of the length thereof located below the horizontal level of said ridge and the remainder thereof located not substantially higher than said ridge to maintain said passage filled with stock through the full speed range of operation of said head box, means forming a bleed chamber in said head box located forwardly of said ridge, means defining a slot in said top wall adjacent said constriction and below said bleed chamber and extending substantially the full width of said discharge passage for conducting air bubbles from the stock in said discharge passage to said bleed chamber, and means for venting said bleed chamber.

10. A head box for a Fourdrinier paper machine having a forming wire and a breast roll supporting the wire in a predetermined horizontal plane, comprising walls defining a main chamber for receiving the paper making stock, means including a bottom wall forming a ridge extending permanently across said main chamber and defining therewith a rear and a front compartment, means for delivering stock into said rear compartment for flow therefrom over said ridge to said front compartment, means forming a slice in substantially the same horizontal plane as the wire for delivering the stock from said front compartment to the wire, means including a top wall forming a discharge passage leading from said front compartment to said slice, means establishing said ridge at substantially the same horizontal level as the wire to provide for slow speed cooperation of said head box with a correspondingly low pressure head of stock above said ridge, removable partition means above said ridge for raising the height. of said front compart a substantial portion of the length thereof located below the horizontal level of said ridge and the remainder thereof located not substantially higher than said ridge to maintain said distributor roll submerged in stock through the full speed range of operation of said head box, means forming a bleed chamber in said head box located forwardly of said ridge, means defining a slot in said top wall located adjacent said constriction and extending substantially the full width of said discharge passage for conducting air bubbles from the stock in said discharge passage to said bleed chamber, and means for venting said bleed chamber.

11.. A headbox for a Fourdrinier paper machine having a forming Wire and a breast roll supporting the wire in a predetermined horizontal plane, comprising front and rear walls and a pair of side walls defining a main chamber for receiving the paper making stock, said chamber being open to atmospheric pressure at the top thereof, means forming a partition extending across said main chamber and defining therein a rear and a front compartment, means defining a stock inlet chamber adjacent the bottom end of said rear compartment, means defining an inlet slot connecting said inlet chamber with said rear compartment and of materially lesser flow area than said inlet chamber and said rear compartment, the lower portions of opposed walls of said rear compartment being arranged to diverge upwardly from the opposed edges of said slot, an imperforate baffle within the bottom end of said rear compartment mounted between said diverging walls above and in controlling relation with said inlet slot, said bafile being of generally inverted teardrop shape in cross section providing a substantially semi-cylindrical lower face and upper side faces converging to an apex, means maintaining said bafile with said apex pointing upwardly to cause sudden acceleration of the stock flow past the lower end thereof followed by gradual deceleration of the stock flow to and past said apex, and means for adjusting said bafile towards and away from said slot to vary the effective flow area therepast.

References Cited in the file of this patent UNITED STATES PATENTS 1,534,080 Russell Apr. 21, 1925 1,727,928 Berry Sept. 10, 1929 1,775,905 Lang Sept. 16, 1930 1,886,607 Wood July 12, 1932 1,898,372 Hyde Feb. 1, 1933 1,909,150 Bell-Irving et al May 16, 1933 2,062,471 Murray Dec. 1, 1936 2,118,491 Chuse May 24, 1938 2,202,890 Berry June 4, 1940 2,205,693 Miline June 25, 1940 2,284,098 Lang May 26, 1942 2,308,370 Kellett et al. Jan. 12, 1943 2,325,016 Warren July 20, 1943 2,329,799 Thorsen Sept. 21, 1943 2,339,730 Vedder et al. Jan. 18, 1944 2,381,286 Hornbostel et al. Aug. 7, 1945 (Other references on following page) 1 1 UNITED STATES PATENTS 2 Osgood May 9, 1950 V 31 Hornbostel May 30, 1950 7 Lowe Aug. 7, 1951 r 5; Heys May 4, 1954 a 8 Goumeniouk May 11, 1954 6.817549 FOREIGN PATENTS Germany May 20, 1910 Germany Oct. 1, 1910 Q d 31, Germany Dec. 17, 1912 a 12 Ital-y Oct. 8, 1927 Great Britain July 23, 1931 Germany Nov. 25, 1931 Great Britain Nov. 7,1951 Great Bricain May 21, 1952 Great Britain Oct. 29, 1952 OTHER REFERENCES Mac'Naughton: Paper Trade 1., Dec. 26, 1940, pp. 30

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,870,690 January 27, 1959 Wesley S. Corbin et al, I

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters .Patent should readas corrected below.

Column 5, line 65, for "increasing" read increased column 6, line 4, for "rolls" read roll column 10, line 61, list of referencefi cited, under the heading "UNITED STATES PATENTS", for the patent number "1,886,607" read 1,866,607

Signed and sealed this 9th day of June 1959.

SEAL) t'test:

KARL AXLINE ROBERT c. WATSON Attesting Oflicer Commissioner of Patents i I I I 1

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