Headbox with variable eddy decay length

Claim 2

In a headbox comprising opposed slice blades defining a slice chamber having at the downstream end thereof a slice opening of variable area for feeding paper making stock to a forming member, paper making stock supplying means, a flow channel having an upstream end receiving paper making stock from said paper making stock supply means and a downstream end discharging said paper making stock into said slice chamber, said flow channel having a flow area defined by first, relatively long, opposed boundaries extending in the cross machine direction of said headbox and constituting the width of said flow channel and second, relatively short, opposed boundaries extending between said first opposed boundaries and defining the depth of said flow channel, and means subdividing said flow channel into a plurality of passages to create a corresponding plurality of eddies as the stock passes from said passages into said slice chamber, the improvement comprising means for selectively varying the velocity of flow through said flow channel and the decay length of said eddies, comprising: means movable across said flow area of said flow channel for changing the effective distance between said first boundaries and the depth of said flow channel by blocking or uncovering portions of said flow channel progressively along a line parallel to said first boundaries.

Claim 3

The headbox of claim 1 wherein said movable means is associated with one of said blades and movable therewith.

Claim 4

The headbox of claim 1 wherein said subdividing means comprises a plurality of tubular members arranged in a plurality of rows extending in said cross machine direction, and said movable means comprises means for closing or opening simultaneously all said passages in rows thereof.

Claim 5

The headbox of claim 1 wherein said slice blades include a nozzle blade, and said nozzle blade is pivotally mounted on said movable means for pivotal movement of said nozzle blade independently of movement of said movable means.

Claim 6

The headbox of claim 1 wherein said slice blades include a pivotally mounted nozzle blade and an apron blade, and said apron blade is fixed with respect to said movable means.

Claim 7

A headbox comprising: a. a stock supply chamber for supplying stock at a predetermined head, b. a plurality of tubular means defining a flow channel composed of a corresponding plurality of passages communicating with said stock supply chamber at the upstream end thereof, c. said tubular means being arranged in a plurality of rows with said rows extending in the cross machine direction of said headbox, d. a nozzle blade pivotally mounted along one edge thereof adjacent the downstream end of an outermost one of said rows of tubular means, e. an apron blade extending in opposed relationship to said nozzle blade adjacent the downstream end of the other of said outermost rows of tubular means and cooperating with said nozzle blade to define a slice chamber leading to a discharge slot between the downstream ends of said blades, and f. means for controlling the decay length of the eddies created by discharge of stock from said plurality of passages into the upstream end of said slice chamber, further comprising, i. mounting means associated with said nozzle and apron blades extending substantially perpendicularly with respect to said flow channel, ii. means defining a slotted opening formed in said mounting means for one of said blades, and iii. fastening means extending through said slotted opening to provide for sliding movement of said slotted mounting means across the downstream end of said flow channel for progressively covering the downstream ends of said rows of passages and thereby increasing the velocity through the remaining uncovered passages and the decay length of said eddies.

Claim 8

A headbox comprising: a. a stock supply chamber for supplying stock at a predetermined head, b. a plurality of tubular means defining a flow channel composed of a corresponding plurality of passages communicating with said stock supply chamber at the upstream end thereof, c. said tubular means being arranged in a plurality of rows with said rows extending in the cross machine direction of said headbox, d. a nozzle blade pivotally mounted along one edge thereof adjacent the downstream end of an outermost one of said rows of tubular means, e. an apron blade extending in opposed relationship to said nozzle blade adjacent the downstream end of the other of said outermost rows of tubular means and cooperating with said nozzle blade to define a slice chamber leading to a discharge slot between the downstream ends of said blades, and f. means for controlling the decay length of the eddies created by discharge of stock from said plurality of passages into the upstream end of said slice chamber, further comprising, i. mounting means associated with said nozzle and apron blades extending substantially perpendicularly with respect to said flow channel, ii. means defining a slotted opening formed in said mounting means for one of said blades, and iii. fastening means extending through said slotted opening to provide for sliding movement of said slotted mounting means across the downstream end of said flow channel for progressively covering the downstream ends of said rows of passages and thereby increasing the velocity through the remaining uncovered passages and the decay length of said eddies.