Headbox

Claim 2

A headbox comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through the headbox; - an outlet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet chamber and said outlet chamber to establish a fluid path from said inlet chamber to said outlet chamber, said diffuser including a plurality of conduits in fluid communication with said inlet and outlet chambers, each conduit being divided in at least two successive portions, referenced as a first portion and a second portion establishing first and second fiber suspension passages respectively, said first passage having a smaller cross-sectional area than said second passage, each of said conduits including an elongated stem mounted therein, said first passage being defined between said stem and an inner wall of said conduit, said first passage defining in cross-section a multiply connected domain; and - an abrupt transition between said passages, said abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit.

Claim 3

A headbox as defined in claim 1, wherein said second portion is free of said stem.

Claim 4

A headbox as defined in Claim 1 or Claim 2, wherein said stem has a stepped structure of diminishing cross-sectional area in the direction of fiber suspension flow in said conduit.

Claim 5

A headbox as defined in any preceding claim, further comprising a channel structure in said stem to supply fiber suspension from said inlet chamber to said first passage, said channel structure comprising an inlet portion in fluid communication with said inlet chamber and a plurality of branches leading from said inlet portion to said first passage.

Claim 6

A headbox as defined in claim 4, wherein each branch forms a right angle with a longitudinal axis of said inlet portion.

Claim 7

A headbox as defined in Claim 4 or Claim 5, wherein said channel structure is T shaped.

Claim 8

A headbox as defined in claim 4, wherein each branch defines an obtuse angle with a longitudinal axis of said inlet portion.

Claim 9

A headbox as defined in claim 4, wherein said branches are generally parallel with said inlet portion.

Claim 10

A headbox, comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through the headbox; - an outlet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet chamber and outlet chamber to establish a fluid path therebetween, said diffuser including a plurality of conduits in fluid communication with said inlet and outlet chambers, each conduit including at least two successive portions, namely a first portion and a second portion establishing first and second fiber suspension passages respectively, of larger cross-sectional area in the direction of flow of fiber suspension through said conduit, said first passage defining in cross-section a multiply connected domain; and - an abrupt transition between said passages constituting means to create a vortex in the fiber suspension flow through said conduit.

Claim 11

A headbox, comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through the headbox; - an outlet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet chamber and outlet chamber to establish a fluid path therebetween, said diffuser including a plurality of conduits in fluid communication with said inlet and outlet chambers, each conduit including at least two successive portions, namely a first portion and a second portion establishing first and second fiber suspension passages respectively, of larger cross-sectional area in the direction of flow of fiber suspension through said conduit, said first passage defining in cross-section a multiply connected domain; and - an abrupt transition between said passages constituting means to create a vortex in the fiber suspension flow through said conduit.

Claim 12

A headbox as defined in claim 9, wherein said first passage is ring shaped in cross-section.

Claim 13

A headbox as defined in claim 9, wherein said second passage is generally cylindrical in cross-section.

Claim 14

A headbox comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through the headbox; - an oulet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path therebetween, said diffuser including a plurality of conduits in fluid communication with said chambers, each conduit including at least two successive portions establishing respective fiber suspension passages of larger cross-sectional area in the direction of fiber suspension flow through said conduit, a stem mounted in each of said conduits, one of said passages being defined between said stem and an inner wall of said conduit, said one of said passages defining in cross-section a multiply connected domain; and - an abrupt transition between said passages, said abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit.

Claim 15

A headbox comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through the headbox; - an oulet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path therebetween, said diffuser including a plurality of conduits in fluid communication with said chambers, each conduit including at least two successive portions establishing respective fiber suspension passages of larger cross-sectional area in the direction of fiber suspension flow through said conduit, a stem mounted in each of said conduits, one of said passages being defined between said stem and an inner wall of said conduit, said one of said passages defining in cross-section a multiply connected domain; and - an abrupt transition between said passages, said abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit.

Claim 16

A headbox comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through the headbox; - an outlet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path between said chambers, said diffuser including a plurality of conduits in fluid communication with said chambers, each conduit being divided in at least two successive portions establishing respective fiber suspension passages of larger cross-­sectional area in the direction of fiber suspension flow through said conduit, one of said passages defining, in cross-section, a multiply connected domain; and - an abrupt transition between said passages, said abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit.

Claim 17

A headbox comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through the headbox; - an outlet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path between said chambers, said diffuser including a plurality of conduits in fluid communication with said chambers, each conduit being divided in at least two successive portions establishing respective fiber suspension passages of larger cross-­sectional area in the direction of fiber suspension flow through said conduit, one of said passages defining, in cross-section, a multiply connected domain; and - an abrupt transition between said passages, said abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit.

Claim 18

A headbox, comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through said headbox; - an outlet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path therebetween, said diffuser including a plurality of conduits in fluid communication with said inlet and outlet chambers, each conduit having a predetermined internal volume and including an elongated member received in an initial portion of said conduit, said elongated member filling partially said internal volume to establish in said conduit an initial passage and at least one additional passage downstream of said initial passage, said initial passage having a smaller cross-sectional area than said additional passage and being separated therefrom by an abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit, said initial passage being defined between said stem and an inner wall of said conduit, said initial passage defining in cross-section a multiply connected domain.

Claim 19

A headbox, comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through said headbox; - an outlet chamber downstream of said inlet chamber, said outlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path therebetween, said diffuser including a plurality of conduits in fluid communication with said inlet and outlet chambers, each conduit having a predetermined internal volume and including an elongated member received in an initial portion of said conduit, said elongated member filling partially said internal volume to establish in said conduit an initial passage and at least one additional passage downstream of said initial passage, said initial passage having a smaller cross-sectional area than said additional passage and being separated therefrom by an abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit, said initial passage being defined between said stem and an inner wall of said conduit, said initial passage defining in cross-section a multiply connected domain.

Claim 20

A headbox, as defined in claim 14, including channel means in said elongated member to establish a fluid communication between said inlet chamber and said initial passage.

Claim 21

A headbox, as defined in Claim 14 or Claim 15, wherein said additional passage is free of said elongated member.

Claim 22

A headbox, as defined in any one of Claims 14 to 16, wherein said elongated member has a stepped structure of diminishing cross-sectional area in the direction of fiber suspension flow in said conduit.

Claim 23

A headbox, comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through said headbox; - an outlet chamber downstream of said inlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path therebetween, said diffuser having a plurality of conduits in fluid communication with said inlet and outlet chambers, each conduit having a predetermined internal volume and comprising: i) an elongated member mounted in said conduit for filling partially said internal volume to define in said conduit two successive passages of different cross-­sectional areas, referenced as a first passage and a second passage, said first passage being defined between said elongated member and an inner wall of said conduit and having a smaller cross-sectional area than said second passage; ii) between said passages a zone of abrupt transition from one cross-sectional area value to another, said zone of abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit; iii) channel means in said elongated member to establish a fluid communication between said passages and said inlet chamber.

Claim 24

A headbox, comprising: - an inlet chamber communicating with a source of fiber suspension, said fiber suspension having a direction of flow through said headbox; - an outlet chamber downstream of said inlet chamber comprising a discharge opening; - a diffuser mounted between said inlet and outlet chambers to establish a fluid path therebetween, said diffuser having a plurality of conduits in fluid communication with said inlet and outlet chambers, each conduit having a predetermined internal volume and comprising: i) an elongated member mounted in said conduit for filling partially said internal volume to define in said conduit two successive passages of different cross-­sectional areas, referenced as a first passage and a second passage, said first passage being defined between said elongated member and an inner wall of said conduit and having a smaller cross-sectional area than said second passage; ii) between said passages a zone of abrupt transition from one cross-sectional area value to another, said zone of abrupt transition constituting means to create a vortex in the flow of fiber suspension through said conduit; iii) channel means in said elongated member to establish a fluid communication between said passages and said inlet chamber.

Claim 25

A headbox as defined in claim 1, wherein a major portion of each of said conduits is substantially free of a restriction.