Extensional flow mixer

An extensional flow mixer suitable for high viscosity liquids such as plastic materials, comprising:

• a housing (10) with a cylindrical cavity having a side wall (11);
• an axial inlet (12a) into said cavity at one end of said housing and connectable to a pressurized source of the liquids;
• an outlet (19) for the mixed liquids leading from the cavity, said outlet being at the center of an outlet end of the housing opposite said one end;
• a first die member (20) in said cavity at said outlet end of said housing;
• said first die member carrying annular concentric protrusions (20′) surrounding a central aperture (20a) which communicates with the outlet;
• a mandrel (30) located in said cavity, a second die member (32) fixed to said mandrel and carrying annular, concentric protrusions (32′), the protrusions of the first die member having inner edges symmetrically opposed inner edges of the second die member, and said protrusions having sloping side surfaces to divide the space between the die members into a series of annular chambers (C1,C2, . . . ) separated by annular slits between said inner edges, with said sloping side surfaces providing convergent entrances to, and divergent exits from, the slits;
• means (22,23) for adjusting the position of one of said die members in the housing to alter the slit gaps;
• characterized in that said mandrel has sides provided with helical grooves (34) and has radial passageways (36) connecting said helical grooves to said inlet, said grooves forming helical passageways with said side wall (11), said passageways communicating with outer edges of said die members for distributing the liquids around the edges of the die members.

An extensional flow mixer suitable for liquids such as plastic materials, of the type comprising:

• a housing (110) defining cavity having an internal surface (111b) connecting ends of the cavity, the housing having an inlet (I 12a) into one end of said cavity and connectable to a pressurized source of the liquids and having an axial outlet (119) for the mixed liquids leading from the end of the cavity opposite said one end,
• a mandrel (130) rotatable in said cavity, said mandrel carrying co-axial protrusions (132) having side surfaces which converge towards outer edges of the protrusions, said outer edges cooperating with said internal surface (111b) of the cavity to define slits such that liquid passes through said slits in moving from the inlet to the outlet, said side surfaces providing convergent entrances to, and divergent exits from, the slits,
• characterized in that said cavity is frusto-conical having a large end at said inlet (112a) and a small end at said outlet,
• and in that said protrusions (132) are annular, and are such that said outer edges divide the space between the protrusions and the internal surface into a series of annular chambers (C1,C2,C3,C4) separated by said slits such that liquid passes successively through all said chambers and said slits in moving from the inlet to the outlet,
• said chambers having a mean diameter which decreases from an outermost chamber adjacent the inlet to an innermost chamber adjacent the outlet.