Extrusion mill

Claim 2

In a mill for mixing and extruding elastomeric stock, said mill including a barrel having an elongate bore, and a worm rotatably supported in said bore, said worm in axial crosssection presenting helical threads and grooves alternating with one another and which are adapted to mix and advance elastomeric stock in said bore, said threads terminating in respective crests which extend adjacent to an internal surface of said barrel defining said bore, each of said crests having frontal and distal portions facing downstream and upstream of said bore, respectively, an improvement comprising deaerating means for venting-to-atmosphere only unidirectionally upstream of said bore fluid collected in the latter from elastomeric stock mixed by said worm, said deaerating means defining a helical venting path between said internal surface of said barrel and said distal portion of each of said crests, said helical venting path having a maximum radial clearance which is greater than any clearance between said internal surface of said barrel and said frontal portion of each of said crests, each of said grooves having a tapered bottom which deepens in a direction downstream of said bore, the more shallow upstream region of each said tapered bottom acting to compress and deaerate elastomeric stock, the deeper downstream region of each said tapered bottom permitting fluid deareated from the elastomeric stock to advance downstream to said helical venting path.

Claim 3

In a mill as claimed in claim 1, wherein said distal portion of each of said crests is formed with a helical cut-out which radially deepens in a direction upstream of said bore, said cut-out helically extending uniformly along said crests and cooperatively with said internal surface of said barrel defining said helical venting path.

Claim 4

In a mill as claimed in claim 2, wherein said cut-out has an extent axially of said bore which is in the range of approximately 0.25-0.50 times the thickness of said crests axially of said bore.

Claim 5

In a mill as claimed in claim 2, wherein said cut-out has a depth of at least 1.25 times greater than any clearance between said frontal portion of each of said crests and said internal surface of said barrel.

Claim 6

In a mill as claimed in claim 2, wherein said cut-out is in the form of a bevel.

Claim 7

In a mill as claimed in claim 5, wherein said bevel is inclined at an angle in the range of approximately 10*-30*.

Claim 8

In a mill as claimed in claim 2, wherein said cut-out is in the form of a step.

Claim 9

In a mill as claimed in claim 1, wherein each of said crests is substantially flat between said frontal and distal portions thereof.

Claim 10

In a mill for mixing and extruding elastomeric stock, said mill including a barrel having an elongate bore, and a worm rotatably supported in said bore, said worm in axial cross-section presenting helical threads and grooves alternating with one another and which are adapted to mix and advance elastomeric stock in said bore, said threads terminating in respective crests which extend adjacent to an internal surface of said barrel defining said bore, each of said crests having frontal and distal portions facing downstream and upstream of said bore, respectively, an improvement comprising deaerating means for venting-to-atmosphere only unidirectionally upstream of said bore fluid collected in the latter from elastomeric stock mixed by said worm, said deaerating means defining a helical venting path between said internal surface of said barrel and said distal portion of each of said crests, said helical venting path having a maximum radial clearance which is greater than any clearance between said internal surface of said barrel and said frontal portion of each of said crests, each of said grooves in succession downstream of said bore having a lesser axial extent and depth than a groove preceding it upstream of said bore, said grooves constituting a group which terminates in a groove having a substantially zero axial extent and depth, each of said threads medially of its respective crest having a conformingly helical thread groove which is greater in depth and axial extent than one preceding it upstream of said bore, said thread grooves in said crests constituting a group which initiates in one having a substantially zero axial extent and depth, the group of thread grooves in said crests overlapping the group of worm grooves.

Claim 11

In a mill for mixing and extruding elastomeric stock, said mill including a barrel having an elongate bore, and a worm rotatably supported in said bore, said worm in axial cross-section presenting helical threads and grooves alternating with one another and which are adapted to mix and advance elastomeric stock in said bore, said threads terminating in respective crests which extend adjacent to an internal surface of said barrel defining said bore, each of said crests having frontal and distal portions facing downstream and upstream of said bore, respectively, an improvement comprising deaerating means for venting-to-atmosphere only unidirectionally upstream of said bore fluid collected in the latter from elastomeric stock mixed by said worm, said deaerating means defining a helical venting path between said internal surface of said barrel and said distal portion of each of said crests, said helical venting path having a maximum radial clearance which is greater than any clearance between said internal surface of said barrel and said frontal portion of each of said crests, each of said grooves in succession downstream of said bore having a lesser axial extent and depth than a groove preceding it upstream of said bore, said grooves constituting a group which terminates in a groove having a substantially zero axial extent and depth, each of said threads medially of its respective crest having a conformingly helical thread groove which is greater in depth and axial extent than one preceding it upstream of said bore, said thread grooves in said crests constituting a group which initiates in one having a substantially zero axial extent and depth, the group of thread grooves in said crests overlapping the group of worm grooves.