Method of making screen media and a screening passage therefore

A method of making a screen for a screen cylinder that filters or screens pulp or fabric fiber in slurry, the method comprising the steps of:

• providing a plate, the plate having a generally planar first surface, a generally planar second surface and a thickness;
• forming in the second surface a plurality of back grooves;
• forming a material relief in each of the plurality of back grooves;
• forming in the first surface a plurality of contour cuts, each contour cut arranged in substantial alignment with a corresponding one of said plurality of back grooves, each contour cut having a bottom defining a residual material between the first surface and the second surface;
• forming a slit through each residual material;
• and wherein each material relief defines a first end wall, a second end wall, and a bottom wall, each of the first end wall and the second end wall are arranged substantially perpendicular to the second surface, and the bottom wall is arranged substantially parallel to the second surface.

A method of making a screen for a screen cylinder that filters or screens a fibrous slurry, the method comprising the steps of:

• (a) providing a plate stock, the plate stock having an inflow surface, an outflow surface and a thickness;
• (b) forming in the outflow surface a plurality of back grooves;
• (c) forming a material relief in each of the plurality of back grooves, each material relief defined by a first end wall and a second end wall;
• (d) forming in the inflow surface a plurality of contour cuts, each contour cut arranged in substantial alignment with a corresponding one of the plurality of back grooves, each contour cut having a bottom defining a residual material between the inflow surface and the outflow surface;
• and thereafter
• (e) forming a slit in the residual material.

A method of making a screen for a screen cylinder that filters or screens a fibrous slurry, the method comprising the steps of:

• providing a plate of metal stock, the plate metal stock having an inflow side on one side, an outflow side on the opposite side, and a thickness;
• forming in the outflow side a plurality of back grooves using a cutter;
• forming a material relief in each of the plurality of back grooves by end milling, each material relief defining a first end wall, a second end wall and a bottom, each of the first end wall and the second end wall arranged substantially perpendicular to the second surface and the bottom arranged substantially parallel to the second surface;
• forming in the inflow side a plurality of contour cuts using a cutter, each contour cut arranged in substantial alignment with a corresponding one of the plurality of back grooves, each contour cut having a bottom defining a residual material between the first surface and the second surface;
• and
• forming a slit through the residual material from the inflow side.

A method of forming a screening slot in a screen that filters or screens fibrous slurry, the method comprising the steps of:

• (a) providing a plate stock that has an inflow surface and an outflow surface;
• (b) forming a back groove in the outflow surface;
• (c) forming a material relief in the back groove;
• (d) forming a contour inlet in the inflow surface in line with the back groove and defining residual material between the inflow surface and the outflow surface;
• and
• (e) forming a slot in the residual material wherein a screening slit is formed in the residual material where the slot breaks completely through the residual material.

A method of forming a screening slot in a screen that filters or screens fibrous slurry, the method comprising the steps of:

• (a) providing a plate stock that has an inflow surface, an outflow surface, and a cross sectional thickness;
• (b) cutting a back groove in the outflow surface;
• (c) end milling a material relief in a direction parallel to the back groove with the material relief having a pair of end walls;
• (d) cutting a contour cut in the inflow surface in line with the back groove and defining residual material between the inflow surface and the outflow surface;
• and
• (e) cutting a slot in the residual material thereby forming a screening slit in the residual material that extends through the residual material where the slot breaks through the residual material.

A method of forming a screening slot in a screen that filters or screens fibrous slurry, the method comprising the steps of:

• (a) providing a plate stock that has an inflow surface, an outflow surface, and a cross sectional thickness;
• (b) forming a back groove in the outflow surface having a depth of between six and six and one-half millimeters;
• (c) forming a material relief in a direction parallel to the back groove with the material relief having a pair of end walls disposed at an angle relative to one of the inflow surface and the outflow surface of between 70° and 90°;
• (d) forming a contour inlet having a V-shaped cross sectional contour in the inflow surface in line with the back groove with the contour inlet having a depth of about one millimeter and defining residual material between the inflow surface and the outflow surface;
• and
• (e) forming a slot in the residual material using a cutter having a thickness of between 0.05 and 0.7 millimeter and forming a screening slit in the residual material that extends through the residual material where the slot breaks through the residual material.

A method of forming a screening slot in a screen that screens fibrous slurry, the method comprising the steps of:

• (a) providing a plate stock that has an inflow surface and an outflow surface;
• (b) forming a back groove in the outflow surface;
• (c) forming a material relief in a direction parallel to the back groove with the material relief being defined by a surface parallel to one of the inflow surface and the outflow surface and a pair of end walls disposed at an angle relative to one of the inflow surface and the outflow surface and that angle away from each other such that outlet edges of each end wall that are disposed toward the outflow surface are spaced farther apart from each than inlet edges of each end wall that are disposed toward the inflow surface;
• (d) forming a contour inlet having a generally V-shaped cross sectional contour in the inflow surface in line with the back groove and defining residual material between the back groove and the contour inlet;
• (e) forming a slit in the residual material that extends through the residual material;
• (f) wherein the residual material has a substantially uniform thickness substantially along the length of the slit;
• and
• (g) wherein during screening of fibrous slurry, the fibrous slurry flows through the contour inlet, the screening slit, and then the back groove with the screening slit permitting selective passage of fiber therethrough.