Injection molding machine with multichannel wave screw

Claim 2

An injection molding apparatus comprising: a barrel having an inner wall and inlet and outlet openings, a rotatable and reciprocable screw disposed in said barrel means for rotating said screw about its axis and advancing said screw axially in said barrel toward the outlet opening, said screw including a section for enhancing substantially complete melting and mixing of resinous material plasticated by it comprising an outwardly extending conveying flight defining a helical passage, an outwardly extending barrier flight disposed intermediate said conveying flight to divide the helical passage into a pair of flow channels extending side by side helically along said screw section, each of said channels having a base surface whose radius from the screw axis of rotation varies cyclically through a plurality of cycles along the helical length of such channel to provide a channel of varying depth, with the variations of said channels being arranged so that the combined cross-sectional area of said channels is not constant entirely throughout a cycle, the maximum base surface radius portion of the channels on opposite sides of said barrier flight adjacent each area of increasing radius being undercut to provide sufficient clearance between its outermost surface and the inner barrel wall to permit the flow thereover of molten resinous material from the channel having an area of increasing radius to an axially adjacent area of the other channel.

Claim 3

The apparatus according to claim 1 wherein the outer width of said barrier flight lies within a range from about two percent to about eight percent of the screw diameter.

Claim 4

The apparatus of claim 1 wherein the outer edge of said conveying flight extends into such close proximity to the inner barrel wall as to substantially restrict the passage of quantities of solid resinous material therebetween, and wherein said barrier flight and said conveying flight are substantially parallel and have a pitch such that the axial advance of each flight in each 360° about the screw axis is in the range of from about 1.25 to about 1.50 times the diameter described by the outer surface of the conveying flight.

Claim 5

An injection molding apparatus comprising: a barrel having an inner wall and inlet and outlet openings, a rotatable and reciprocable screw disposed in said barrel, means for rotating said screw about its axis and advancing said screw axially in said barrel toward the outlet opening, said scew including a section for enhancing substantially complete melting and mixing of resinous material plasticated by it comprising an outwardly extending conveying flight defining a helical passage, an outwardly extending barrier flight disposed intermediate said conveying flight to divide the helical passage into flow channels extending side by side helically along said screw section, each of the flow channels having a depth which varies cyclically through a plurality of cycles along the helical length of such channel, the minimum depth portions of the flow channels on opposite sides of said barrier flight defining wave crests which are displaced helically from each other, a substantial portion of each channel situated between successive wave crests in the channel being of substantially constant depth, the barrier flight adjacent each wave crest being undercut to provide sufficient clearance between its outermost surface and the barrel inner wall to permit the flow thereover of molten resinous material from the channel containing an area of decreasing depth to an adjacent area of the other channel, the outer width of said barrier flight being thinner than that of the conveying flight so that the shear energy imparted to molten material flowing over the barrier flight is low.

Claim 6

An injection molding apparatus comprising: a barrel having an inner wall and inlet and outlet openings, a rotatable and reciprocable screw disposed in said barrel, means for rotating said screw about its axis and advancing said screw axially in said barrel toward the outlet opening, said scew including a section for enhancing substantially complete melting and mixing of resinous material plasticated by it comprising an outwardly extending conveying flight defining a helical passage, an outwardly extending barrier flight disposed intermediate said conveying flight to divide the helical passage into flow channels extending side by side helically along said screw section, each of the flow channels having a depth which varies cyclically through a plurality of cycles along the helical length of such channel, the minimum depth portions of the flow channels on opposite sides of said barrier flight defining wave crests which are displaced helically from each other, a substantial portion of each channel situated between successive wave crests in the channel being of substantially constant depth, the barrier flight adjacent each wave crest being undercut to provide sufficient clearance between its outermost surface and the barrel inner wall to permit the flow thereover of molten resinous material from the channel containing an area of decreasing depth to an adjacent area of the other channel, the outer width of said barrier flight being thinner than that of the conveying flight so that the shear energy imparted to molten material flowing over the barrier flight is low.

Claim 7

The apparatus according to claim 4 wherein the outer width of said barrier flight lies within a range from about two percent to about eight percent of the screw diameter.

Claim 8

The apparatus of claim 4 wherein the plurality of wave cycles in one flow channel corresponds to the plurality of wave cycles in the other flow channel so that the flow restriction presented by both flow channels is the same.

Claim 9

The injection apparatus according to claim 4 wherein each wave cycle has a helical length that extends 180° about the screw axis and wherein the screw section is operable in conjunction with the barrel to pressurize the synthetic resinous material.

Claim 10

The apparatus according to claim 4 wherein there are at least three wave cycles in each flow channel for each pitch length of the helical passage.

Claim 11

The apparatus according to claim 4 wherein there is an integral number of wave cycles in each flow channel for each pitch length of the helical passage so as to balance side forces exerted on the screw by the synthetic resinous material during operation.

Claim 12

The apparatus of claim 4, wherein each of said channel cycles includes an area of increasing channel depth, an area of decreasing channel depth, and an area of constant channel depth, and wherein each wave crest in one of the channels is disposed adjacent an area of constant depth in the other channel.

Claim 13

An injection molding apparatus comprising: a barrel having an inner wall and inlet and outlet openings, a rotatable and reciprocable screw disposed in said barrel, means for rotating said screw about its axis and advancing said screw axially in said barrel toward the outlet opening, said screw including a section for enhancing substantially complete melting and mixing of resinous material plasticated by it comprising outwardly extending conveying flight means defining a helical passage, outwardly extending barrier flight means disposed intermediate said conveying flight means to divide the helical passage into flow channels extending side by side helically along said screw section, each of the flow channels having a depth which varies cyclically through a plurality of cycles along the helical length of such channel, the minimum depth portions of the flow channels on opposite sides of said barrier flight means defining wave crests which are displaced helically from each other, and the barrier flight means adjacent each wave crest being undercut to provide sufficient clearance between its outermost surface and the barrel inner wall to permit the flow thereover of molten resinous material from the channel having an area of decreasing depth to an adjacent area of the other channel, the outer width of said barrier flight means being thinner than that of said conveying flight means and being less than eight percent of the screw pitch, so that the shear energy imparted to molten material flowing over said barrier flight means is low.

Claim 14

An injection molding apparatus comprising: a barrel having an inner wall and inlet and outlet openings, a rotatable and reciprocable screw disposed in said barrel, means for rotating said screw about its axis and advancing said screw axially in said barrel toward the outlet opening, said screw including a section for enhancing substantially complete melting and mixing of resinous material plasticated by it comprising outwardly extending conveying flight means defining a helical passage, outwardly extending barrier flight means disposed intermediate said conveying flight means to divide the helical passage into flow channels extending side by side helically along said screw section, each of the flow channels having a depth which varies cyclically through a plurality of cycles along the helical length of such channel, the minimum depth portions of the flow channels on opposite sides of said barrier flight means defining wave crests which are displaced helically from each other, and the barrier flight means adjacent each wave crest being undercut to provide sufficient clearance between its outermost surface and the barrel inner wall to permit the flow thereover of molten resinous material from the channel having an area of decreasing depth to an adjacent area of the other channel, the outer width of said barrier flight means being thinner than that of said conveying flight means and being less than eight percent of the screw pitch, so that the shear energy imparted to molten material flowing over said barrier flight means is low.

Claim 15

The apparatus according to claim 11 wherein some of the upstream wave crests of each channel provide greater clearance than some of the downstream wave crests of the same channel to accommodate passage of larger concentrations of unmelted material.

Claim 16

The apparatus of claim 11, wherein the outer edge of said conveying flight means extends into such close proximity to the inner barrel wall as to substantially restrict the passage of quantities of solid resinous material therebetween, and wherein said barrier flight means and conveying flight means are substantially parallel and have a pitch such that the axial advance of each flight means in each 360° degrees about the screw axis is in the range of from about 1.25 to about 1.50 times the diameter described by the outer surface of the conveying flight means.

Claim 17

The apparatus according to claim 11 wherein said channel cycles each include an area of increasing base surface radius, an area of decreasing base surface radius, and an area of constant base surface radius, wherein each maximum base surface radius portion in one channel is disposed adjacent an area of constant base surface radius in the other channel.

Claim 18

The apparatus according to claim 11 wherein the outer width of said barrier flight means lies within a range from about two percent to about eight percent of the screw diameter.

Claim 19

The apparatus of claim 15 wherein the clearance between the outermost surface of said barrier flight means and the inner wall of said barrel is in the range of from about 40% to about 100% of the clearance between the wave crests and the inner wall of the barrel.

Claim 20

The apparatus according to claim 11 wherein the clearance between the inner wall of the barrel and a substantial number of said wave crests is in the range of from about 0.03 to about 0.15 times the square root of the diameter of the inner wall of the barrel.

Claim 21

The apparatus of claim 17 wherein the maximum depth of a channel is in the range of from about 2.5 to about 5 times the minimum depth of a channel.

Claim 22

The apparatus according to claim 11 wherein each cycle of each channel is asymmetrical in that the extent of an area of increasing radius is less than the extent of decreasing radius of the cycle.

Claim 23

The apparatus according to claim 19 wherein the base surface radius of each channel is continuously varying in the helical direction throughout the length of a cycle.

Claim 24

An injection molding machine according to claim 1 wherein the screw section is operable in conjunction with the barrel to pressurize the synthetic resinous material.

Claim 25

An injection molding machine according to claim 21 wherein there is an integral number of wave cycles in each flow channel for each pitch length of the helical passage so as to balance side forces exerted on the screw by the synthetic resinous material during operation.

Claim 26

An injection molding machine according to claim 11 wherein there is an integral number of wave cycles in each flow channel for each pitch length of the helical passage so as to balance side forces exerted on the screw by the synthetic resinous material during operation.

Claim 27

An injection molding machine according to claim 23 wherein the plurality of wave cycles in the one flow channel corresponds to the plurality of wave cycles in the other flow channel so that the flow restriction presented by both flow channels is the same.

Claim 28

An injection molding machine according to claim 23 wherein each wave cycle has a helical length that extends 180° about the screw axis and wherein the screw section is operable in conjunction with the barrel to pressurize the synthetic resinous material.

Claim 29

An injection molding machine according to claim 23 wherein there are at least three wave cycles in each flow channel for each pitch length of the helical passage.