Paper machine headbox having convergent throat portion

Claim 2

In a headbox for supplying a stock suspension to a machine slice of a web forming machine at substantially uniform velocity profile, a distributor section having an elongated tapered header extending in a cross machine direction to receive stock from a stock supply, a mixing chamber of substantially uniform shallow depth A throughout the length thereof, extending across the machine and connected to the header by a plurality of substantially uniformly spaced flow connection pipes of small diameter directly entering one face of the mixing chamber adjacent the chamber back wall to provide in operation a zone of sudden flow expansion with succEeding impingement of stock against the opposing chamber face spaced said distance A therefrom, with consequent increase in macro turbulence, said mixing chamber faces converging to a throat portion of depth E spaced a distance L from the chamber back wall and diverging in a downstream direction at an angle of divergence of not more than 7* to provide diffusion of the suspension, the ratio of mixing chamber length to depth, L/A, being equal to or greater than 6 and the ratio of mixing chamber depth to throat depth, A/E, being greater than 3.

Claim 3

In a headbox for supplying a stock suspension to a machine slice of a web forming machine at substantially uniform velocity profile, a distributor section having an elongated tapered header extending in a cross machine direction to receive stock from a stock supply, a mixing chamber of substantially uniform shallow depth A throughout the length thereof, extending across the machine and connected to the header by a plurality of flow connection pipes of diameter D substantially uniformly spaced at centre distances C directly entering one face of the mixing chamber adjacent the chamber back wall to provide in operation a zone of sudden flow expansion with succeeding impingement of stock against the opposing chamber face spaced said distance A therefrom, with consequent increase in macro turbulence before flowing to a convergent exit throat portion of depth E spaced a distance L from the chamber back wall havig a portion of a said chamber face inclined convergingly in the direction of flow towards the chamber other face at an angle in the range 35* to 55*, the ratio of mixing chamber length to depth, L/A, being equal to or greater than 6, the ratio of mixing chamber depth to throat depth, A/E being greater than 3, and the diffusion ratio N of stock flow entering the mixing chamber, where N A X C/ 1/4 pi D2, is from about 1.9 to 3.5.

Claim 4

In a headbox for supplying a stock suspension to a machine slice of a web forming machine at substantially uniform velocity profile, a distributor section having an elongated tapered header extending in a cross machine direction to receive stock from a stock supply, a mixing chamber of substantially uniform shallow depth A throughout the length thereof, extending across the machine and connected to the header by a plurality of flow connection pipes of diameter D substantially uniformly spaced at centre distances C directly entering one face of the mixing chamber adjacent the chamber back wall to provide in operation a zone of sudden flow expansion with succeeding impingement of stock against the opposing chamber face spaced said distance A therefrom, with consequent increase in macro turbulence before flowing to a convergent exit throat portion of depth E spaced a distance L from the chamber back wall havig a portion of a said chamber face inclined convergingly in the direction of flow towards the chamber other face at an angle in the range 35* to 55*, the ratio of mixing chamber length to depth, L/A, being equal to or greater than 6, the ratio of mixing chamber depth to throat depth, A/E being greater than 3, and the diffusion ratio N of stock flow entering the mixing chamber, where N A X C/ 1/4 pi D2, is from about 1.9 to 3.5.

Claim 5

The head box as claimed in claim 2 having transfer passage means positioned in flow rectifying relation between said exit throat and an outlet slice, having a load bearing structural means located external thereto to substantially resist bending forces in the cross-machine direction, and maintain an adjacent wall of the transfer passage means substantiallly undeformed in operation, and a plurality of load transfer partition means in spaced relation across the width of the headbox, extending longitudinally in the direction of stock flow and securing said adjacent wall to the passage wall opposite thereto in load transfer relation, to maintain the transfer passage means substantially undeformed during operation under hydraulic pressure forces of stock flowing therethrough.

Claim 6

The headbox as claimed in claim 3 having a pair of lips defining said slice attached to said rectifier means, in load transfer relation therewith, to maintain the inlet flow area to the slice substantially constant for all working conditions of the box.

Claim 7

The headbox as claimed in claim 4 having one said slice lip secured in pivotal relation to said rectifier means, and first adjustment means to control the inclination of said slice lip relative to the other lip of the slice.

Claim 8

The headbox as claimed in claim 5, including a second slice adjustment means including a lip extension portion slidably attached to a said slice lip and slidably movable in closing relation.