US4740342A — Thermoforming flexible plastic foam shells

Claim 1

Independent Claim 192 words

A method for producing a formed foam shell in an ethylene-containing foam sheet material, the method comprising: (a) providing a closed cell ethylene-containing foam sheet having an initial thickness of 0.050-0.250 inch; (b) rapidly radiant heating said foam sheet to a temperature of 130°-250° F.; and (c) die forming a central portion of the heated foam sheet to produce a desired concave shaped shell having a depth at least about 10 times the foam initial thickness, said die forming being performed by cooperating die units having mating sheet engaging shaped surfaces and effecting relative movement between said die units to bring said shaped surfaces into engagement with said sheet and into mating relationship with one another, rapidly cooling the shaped foam material to below its plastic transition temperature during the die forming by contacting the sheet with a forming die unit which is cooled to below the heated foam temperature, so as to produce a stable shaped shell within a central portion of the foam sheet in a heating and die forming cycle time of 2-6 seconds, said shell having a thickness at least about 30% of the foam sheet initial thickness.

Claim 2

Independent Claim 192 words

A method for producing a formed foam shell in an ethylene-containing foam sheet material, the method comprising: (a) providing a closed cell ethylene-containing foam sheet having an initial thickness of 0.050-0.250 inch; (b) rapidly radiant heating said foam sheet to a temperature of 130°-250° F.; and (c) die forming a central portion of the heated foam sheet to produce a desired concave shaped shell having a depth at least about 10 times the foam initial thickness, said die forming being performed by cooperating die units having mating sheet engaging shaped surfaces and effecting relative movement between said die units to bring said shaped surfaces into engagement with said sheet and into mating relationship with one another, rapidly cooling the shaped foam material to below its plastic transition temperature during the die forming by contacting the sheet with a forming die unit which is cooled to below the heated foam temperature, so as to produce a stable shaped shell within a central portion of the foam sheet in a heating and die forming cycle time of 2-6 seconds, said shell having a thickness at least about 30% of the foam sheet initial thickness.

Claim 3

Dependent Claim 52 words

The method of claim 1, wherein said foam sheet heating is performed by intermittently moving the sheet between adjacent radiant heating surfaces, said heating surfaces being located on each side of the foam sheet, and maintained at 400°-700° F. temperature, so as to produce a foam sheet heating rate of 3°-60° F./sec.

Claim 4

Dependent Claim 42 words

The method of claim 1, wherein said foam sheet heating is performed in 2 or three successive steps, the foam sheet being heated to 130°-200° F. in a first heating step, then successively heated to 200°-250° F. in a final heating step.

Claim 5

Dependent Claim 55 words

The method of claim 1, wherein the heated foam sheet is intermittently moved and clamped between the forming die unit which stabilizes the shell edges, and the die unit includes a body and plug which are cooled by circulating a coolant through flow passages therein while forming the concave shaped shell within the foam sheet.

Claim 6

Dependent Claim 23 words

The method of claim 1, wherein the die formed shell has a depth 12-25 times the initial thickness of the foam sheet material.

Claim 7

Dependent Claim 64 words

The method of claim 1, wherein said die forming step includes withdrawing air from below the foam sheet to partially deform the sheet into a lower cavity of the forming die unit, plug forming the foam sheet further downwardly, and air pressurizing the foam concave shape around the plug to provide additional lateral forming of the foam sheet into the die unit lower cavity.

Claim 8

Dependent Claim 22 words

The method of claim 1, wherein said heated foam sheet is cooled in the forming die unit at rate of 5°-200° F./second.

Claim 9

Dependent Claim 21 words

The method of claim 1, wherein the foam sheet material is a closed cell polyethylene having initial thickness of 0.060-0.200 inch.

Claim 10

Dependent Claim 17 words

The method of claim 1, wherein 2-10 formed foam shells are produced simultaneously from the foam sheet.

Claim 11

Independent Claim 253 words

A method for producing formed foam shells in an ethylene-containing foam sheet material, the method comprising: (a) providing a closed cell polyethylene-containing foam sheet having an initial thickness of 0.060-0.200 inch; (b) moving said foam sheet intermittently between adjacent radiant heating surfaces and radiant heating the foam sheet from ambient temperature to 130°-250° F. at a heating rate of 3°-60° F./sec.; (c) clamping the heated foam sheet between matched forming die units to stabilize the sheet edges, said die units including a cooperating die unit plug portion and a die unit body portion having mating sheet engaging shaped surfaces, and die forming the heated foam shell sheet by effecting relative movement between said die units to produce a desired concave shaped shell having a draw depth about 12-25 times the initial thickness of the foam sheet, while simultaneously rapidly cooling the die unit plug portion to stabilize the heated foam material during the die forming step and thereby maintaining the formed shell thickness at least about 30% of the foam sheet initial thickness; (d) pressurizing the foam concave shape around the plug to additionally form the foam sheet laterally within the die unit lower cavity; and (e) cooling the die unit body and the plug portions so as to cool the foam sheet at 5°-200° F./sec. to stabilize the formed foam shell, and thereby produce a plurality of shaped foam shells within a central portion of the foam sheet, whereby the foam sheet heating and die forming steps are accomplished at 10-30 cycles/minute.

Claim 12

Independent Claim 253 words

A method for producing formed foam shells in an ethylene-containing foam sheet material, the method comprising: (a) providing a closed cell polyethylene-containing foam sheet having an initial thickness of 0.060-0.200 inch; (b) moving said foam sheet intermittently between adjacent radiant heating surfaces and radiant heating the foam sheet from ambient temperature to 130°-250° F. at a heating rate of 3°-60° F./sec.; (c) clamping the heated foam sheet between matched forming die units to stabilize the sheet edges, said die units including a cooperating die unit plug portion and a die unit body portion having mating sheet engaging shaped surfaces, and die forming the heated foam shell sheet by effecting relative movement between said die units to produce a desired concave shaped shell having a draw depth about 12-25 times the initial thickness of the foam sheet, while simultaneously rapidly cooling the die unit plug portion to stabilize the heated foam material during the die forming step and thereby maintaining the formed shell thickness at least about 30% of the foam sheet initial thickness; (d) pressurizing the foam concave shape around the plug to additionally form the foam sheet laterally within the die unit lower cavity; and (e) cooling the die unit body and the plug portions so as to cool the foam sheet at 5°-200° F./sec. to stabilize the formed foam shell, and thereby produce a plurality of shaped foam shells within a central portion of the foam sheet, whereby the foam sheet heating and die forming steps are accomplished at 10-30 cycles/minute.

Claim 13

Dependent Claim 148 words

A heater assembly for radiantly heating a foam sheet intermittently moving along a processing path, the assembly comprising: (a) an upper heating unit containing a ceramic plate aligned parallel with and located 1-2 inches above the foam sheet processing path, said ceramic plate being heated by an adjacent electrical resistance element mounted above the plate; (b) a lower heating unit containing a ceramic plate aligned parallel with and located 1-2 inches below the foam sheet processing path, said ceramic plate being heated by an adjacent electrical resistance element mounted below the plate, whereby the foam sheet can be moved between the upper and lower heating units for rapid heating of the sheets from both sides thereof; and (c) support means adapted for moving said upper and lower heating units aside whenever intermittent movement of the foam sheet is interrupted, whereby heating of the foam sheet can be interrupted.

Claim 14

Dependent Claim 148 words

A heater assembly for radiantly heating a foam sheet intermittently moving along a processing path, the assembly comprising: (a) an upper heating unit containing a ceramic plate aligned parallel with and located 1-2 inches above the foam sheet processing path, said ceramic plate being heated by an adjacent electrical resistance element mounted above the plate; (b) a lower heating unit containing a ceramic plate aligned parallel with and located 1-2 inches below the foam sheet processing path, said ceramic plate being heated by an adjacent electrical resistance element mounted below the plate, whereby the foam sheet can be moved between the upper and lower heating units for rapid heating of the sheets from both sides thereof; and (c) support means adapted for moving said upper and lower heating units aside whenever intermittent movement of the foam sheet is interrupted, whereby heating of the foam sheet can be interrupted.

Claim 15

Dependent Claim 187 words

A forming die assembly for rapidly forming a foam sheet, comprising: (a) a lower die body containing at least one cavity, said body having flow passages provided therein for flowing a fluid through the body to cool the die body, said cavity having a plurality of passages intersecting the cavity surface; (b) conduit means connected to said passages intersecting said die body cavity for withdrawing air from the cavity; (c) an upper die unit including a frame adapted for clamping the foam sheet against the lower die body; and (d) a plug incorporated into said upper die unit and shaped for mating closely within the cavity of said lower die body, said plug containing flow passages therein for flowing a coolant fluid through the plug to cool the plug, whereby a foam sheet passed between the lower die body and upper die body is deformed downwardly by air withdrawal from the lower die cavity and further formed between the mating body cavity and plug while the sheet is being cooled to below its plastic transition temperature to provide a stable formed shell shape within the foam sheet.

Claim 16

Dependent Claim 187 words

A forming die assembly for rapidly forming a foam sheet, comprising: (a) a lower die body containing at least one cavity, said body having flow passages provided therein for flowing a fluid through the body to cool the die body, said cavity having a plurality of passages intersecting the cavity surface; (b) conduit means connected to said passages intersecting said die body cavity for withdrawing air from the cavity; (c) an upper die unit including a frame adapted for clamping the foam sheet against the lower die body; and (d) a plug incorporated into said upper die unit and shaped for mating closely within the cavity of said lower die body, said plug containing flow passages therein for flowing a coolant fluid through the plug to cool the plug, whereby a foam sheet passed between the lower die body and upper die body is deformed downwardly by air withdrawal from the lower die cavity and further formed between the mating body cavity and plug while the sheet is being cooled to below its plastic transition temperature to provide a stable formed shell shape within the foam sheet.

Claim 17

Dependent Claim 37 words

A forming die assembly according to claim 12, wherein said upper die body is adapted to admit pressurized air adjacent said plug so as to pneumatically form ridges in the sides of a formed plastic foam shell.

Claim 18

Dependent Claim 30 words

A forming die assembly according to claim 12, wherein said lower die body and upper die unit contain 2-6 parallel cavities and mating plugs provided in a close parallel arrangement.

Claim 19

Dependent Claim 39 words

A forming die assembly according to claim 12, wherein the lateral clearance between said upper clamping frame and the mating lower die unit is 0.010-0.090 inch, and the clearance between said cavity and the mating plug is 0.040-0.560 inch.

Claim 20

Dependent Claim 249 words

A forming die assembly for rapidly forming a foam sheet, said assembly comprising: (a) a lower die unit containing at least one cavity, said unit having flow passages provided thereinfor flowing a fluid through the die body to cool the die body, said cavity having a plurality of small passages intersecting the cavity surface; (b) conduit means connected to said passages intersecting said die body cavity for withdrawing air from the cavity; (c) an upper die unit including a frame member adapted for clamping the foam sheet against the lower die body, wherein the clearance between the clamping frame and the mating lower die body is 0.010-0.090 inch; and (d) a die plug incorporated into said upper die unit and shaped for mating closely within the cavity of said lower die body, said plug containing flow passages therein for flowing a coolant fluid through the plug to cool the plug wherein said upper die body is adapted to admit pressurized air adjacent the plug so as to pneumatically form ridges in the sides of a formed plastic foam shell, and the clearance between the plug and the mating lower die cavity is 0.040-0.560 inch; whereby a foam sheet passed between the lower die body unit and upper die unit is deformed downwardly by air withdrawal from the lower die cavity and further formed between the mating body and plug parts, while the sheet is being rapidly cooled to below its plastic transition temperature to provide stable formed shell shapes.

Claim 21

Dependent Claim 249 words

A forming die assembly for rapidly forming a foam sheet, said assembly comprising: (a) a lower die unit containing at least one cavity, said unit having flow passages provided thereinfor flowing a fluid through the die body to cool the die body, said cavity having a plurality of small passages intersecting the cavity surface; (b) conduit means connected to said passages intersecting said die body cavity for withdrawing air from the cavity; (c) an upper die unit including a frame member adapted for clamping the foam sheet against the lower die body, wherein the clearance between the clamping frame and the mating lower die body is 0.010-0.090 inch; and (d) a die plug incorporated into said upper die unit and shaped for mating closely within the cavity of said lower die body, said plug containing flow passages therein for flowing a coolant fluid through the plug to cool the plug wherein said upper die body is adapted to admit pressurized air adjacent the plug so as to pneumatically form ridges in the sides of a formed plastic foam shell, and the clearance between the plug and the mating lower die cavity is 0.040-0.560 inch; whereby a foam sheet passed between the lower die body unit and upper die unit is deformed downwardly by air withdrawal from the lower die cavity and further formed between the mating body and plug parts, while the sheet is being rapidly cooled to below its plastic transition temperature to provide stable formed shell shapes.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-04-26	1991-10-26	1992-04-26	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-04-26	1995-10-26	1996-04-26	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-04-26	1999-10-26	2000-04-26	$7700.00	Window Closed / Lapsed

Thermoforming flexible plastic foam shells

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