Apparatus for extruding plastic material

Claim 2

An extruder comprising a body having a bore, a shaft, said body having an inlet and an outlet adjacent opposite ends of said bore, means for rotatably supporting said shaft in said bore, first helical land means on said shaft extending along its length and defining a main channel for forcing plastic from the inlet toward the other end of the bore upon rotation of the shaft, the lead of said first helical land means increasing at a point downstream from the inlet without change in the transverse cross sectional area of said main channel, second helical land means on said shaft beginning substantially at said point and extending and cooperating with said first helical land means to define an auxiliary channel, said second helical land means having its periphery spaced from the bore a distance greater than said first helical land means at said point such that any molten material in said main channel at said point is permitted to flow freely to said auxiliary channel, said second helical land means terminating in spaced relation to the end of said first helical land means nearest the outlet and having the end thereof in spaced relation to said first helical means, whereby the molten plastic material from said auxiliary channel moves freely back into said main channel and is mixed therewith and moved toward the outlet.

Claim 3

The combination set forth in claim 1 wherein the depth of said main channel decreases in a direction from the beginning toward said point where said auxiliary channel ends.

Claim 4

The combination set forth in claim 1 wherein said main and auxiliary channels have substantially the same depth at said point where said auxiliary channel ends.

Claim 5

The combination set forth in claim 1 wherein said main channel is of substantially the same helical width at least until the point where said auxiliary channel ends.

Claim 6

The combination set forth in claim 1 wherein said main channel is of constant helical width beyond the end of said auxiliary channel.

Claim 7

The combination set forth in claim 1 wherein the helical width of said main channel downstream from said point of increasing lead to the end of said auxiliary channel is at least as great as the helical width of said main channel at the beginning of said increasing lead.

Claim 8

The combination set forth in claim 1 wherein the helical width of said portion of said main channel beyond the end of said auxiliary channel is at least as great as the sum of the helical width of the main channel upstream therefrom and of said auxiliary channel upstream therefrom.

Claim 9

The combination set forth in claim 1 wherein the helical width of said main channel is substantially constant at least until the end of sAid auxiliary channel.

Claim 10

The combination set forth in claim 1 wherein the depth of said main channel decreases uniformly from the point where the auxiliary channel begins to the point where said auxiliary channel ends.

Claim 11

The combination set forth in claim 1 wherein the helical width of said auxiliary channel is constant.

Claim 12

The combination set forth in claim 10 wherein the depth of said auxiliary channel is constant.

Claim 13

The combination set forth in claim 1 wherein the depth of said main channel at a point beyond which said auxiliary channel ends is substantially constant.

Claim 14

An extruder comprising a body having a bore, a shaft said body having an inlet and an outlet adjacent opposite ends of said bore, means for rotatably supporting said shaft in said bore, a first helical land on said shaft extending along its length and defining a main channel for forcing plastic from the inlet toward the other end of the bore upon rotation of the shaft, the lead of said first helical land increasing at a point downstream from the inlet without change in the transverse cross sectional area of said main channel, a second helical land on said shaft beginning substantially at said point and extending and cooperating with said first helical land to define an auxiliary channel, said second helical land having its periphery spaced from the bore a distance greater than said first helical land such that any molten material in said main channel at said point is permitted to flow freely to said auxiliary channel, the depth of said main channel decreasing progressively from the point of beginning of said auxiliary channel where said auxiliary channel ends, said main channel having substantially the same helical width throughout at least until the point where said auxiliary channel ends, the helical width and depth of said auxiliary channel being constant, said second helical land terminating in spaced relation to the end of said first helical land nearest the outlet and having the end thereof in spaced relation to said first helical land, whereby the molten plastic material from said auxiliary channel moves freely back into said main channel and is mixed therewith and moved toward the outlet.

Claim 15

An extruder comprising a body having a bore, a shaft said body having an inlet and an outlet adjacent opposite ends of said bore, means for rotatably supporting said shaft in said bore, a first helical land on said shaft extending along its length and defining a main channel for forcing plastic from the inlet toward the other end of the bore upon rotation of the shaft, the lead of said first helical land increasing at a point downstream from the inlet without change in the transverse cross sectional area of said main channel, a second helical land on said shaft beginning substantially at said point and extending and cooperating with said first helical land to define an auxiliary channel, said second helical land having its periphery spaced from the bore a distance greater than said first helical land such that any molten material in said main channel at said point is permitted to flow freely to said auxiliary channel, the depth of said main channel decreasing progressively from the point of beginning of said auxiliary channel where said auxiliary channel ends, said main channel having substantially the same helical width throughout at least until the point where said auxiliary channel ends, the helical width and depth of said auxiliary channel being constant, said second helical land terminating in spaced relation to the end of said first helical land nearest the outlet and having the end thereof in spaced relation to said first helical land, whereby the molten plastic material from said auxiliary channel moves freely back into said main channel and is mixed therewith and moved toward the outlet.

Claim 16

The combination set forth in claim 13 wherein said main and auxiliary channels are of the same depth at said point where said auxiliary channel ends.

Claim 17

The combination set forth in claim 14 wherein said main channel is of constant width beyond the end of said auxiliary channel.

Claim 18

The combination set forth in claim 13 wherein the helical width of said portion of said main channel beyond the end of said auxiliary channel is at least as great as the sum of the helical width of the main channel upstream therefrom and of said auxiliary channel upstream therefrom.

Claim 19

The combination set forth in claim 13 wherein the depth of said main channel at a point beyond which said auxiliary channel ends is substantially constant.

Claim 20

An extruder comprising a body having a bore, a shaft said body having an inlet and an outlet adjacent opposite ends of said bore, means for rotatably supporting said shaft in said bore, a first helical land on said shaft extending along its length and defining a main channel for forcing plastic from the inlet toward the other end of the bore upon rotation of the shaft, the portion of said land adjacent said inlet defining a feed section, the portion of said land adjacent said outlet defining a metering section, the depth of said main channel decreasing progressively in the intermediate section toward said metering section, the lead of said first helical land increasing at a point downstream from the feed section without change in the transverse cross sectional area of said main channel, a second helical land on said shaft in said intermediate section beginning substantially at said point and extending and cooperating with said first helical means to define an auxiliary channel, said second helical land having its periphery spaced from the bore a distance greater than said first helical means such that any molten material in said main channel at said point is permitted to flow freely from said auxiliary channel, the depth of said main channel decreasing progressively throughout said intermediate section, said main channel having substantially the same helical width throughout said intermediate section, the helical width and depth of said main channel in said intermediate section being at least as great as the helical width and depth of said main channel in said feed section at a point immediately in advance of said point of increasing pitch, the helical width and depth of said auxiliary channel being substantially constant, said main and auxiliary channels having the same depth at said point where said auxiliary channel ends, the helical width of said portion of said main channel beyond the end of said auxiliary channel is at least as great as the sum of the helical widths of the main channel upstream therefrom and of said auxiliary channel upstream therefrom, said helical land terminating in spaced relation to said metering section and having the end thereof in spaced relation to said first helical land, whereby the molten plastic material from said auxiliary channel moves freely back into said main channel and is mixed therewith and moved toward the outlet.

Claim 21

An extruder comprising a body having a bore, a shaft said body having an inlet and an outlet adjacent opposite ends of said bore, means for rotatably supporting said shaft in said bore, a first helical land on said shaft extending along its length and defining a main channel for forcing plastic from the inlet toward the other end of the bore upon rotation of the shaft, the portion of said land adjacent said inlet defining a feed section, the portion of said land adjacent said outlet defining a metering section, the depth of said main channel decreasing progressively in the intermediate section toward said metering section, the lead of said first helical land increasing at a point downstream from the feed section without change in the transverse cross sectional area of said main channel, a second helical land on said shaft in said intermediate section beginning substantially at said point and extending and cooperating with said first helical means to define an auxiliary channel, said second helical land having its periphery spaced from the bore a distance greater than said first helical means such that any molten material in said main channel at said point is permitted to flow freely from said auxiliary channel, the depth of said main channel decreasing progressively throughout said intermediate section, said main channel having substantially the same helical width throughout said intermediate section, the helical width and depth of said main channel in said intermediate section being at least as great as the helical width and depth of said main channel in said feed section at a point immediately in advance of said point of increasing pitch, the helical width and depth of said auxiliary channel being substantially constant, said main and auxiliary channels having the same depth at said point where said auxiliary channel ends, the helical width of said portion of said main channel beyond the end of said auxiliary channel is at least as great as the sum of the helical widths of the main channel upstream therefrom and of said auxiliary channel upstream therefrom, said helical land terminating in spaced relation to said metering section and having the end thereof in spaced relation to said first helical land, whereby the molten plastic material from said auxiliary channel moves freely back into said main channel and is mixed therewith and moved toward the outlet.

Claim 22

The combination set forth in claim 18 wherein the depth of said main channel in said metering section is substantially constant.