Method of molding load-bearing articles from compressible cores and heat malleable coverings

• US 7,837,923 B2
• Filed: 07/16/2008
• Issued: 11/23/2010
• Est. Priority Date: 06/01/2004
• Status: Active Grant

• Current Assignee: Novo Foam Products LLC
• Original Assignee: Novo Foam Products LLC
• Inventors: Lewis, Alan, Hedley, David, Bohan, Thomas, Bearse, Ed
• Primary Examiner(s): WOLLSCHLAGER, JEFFREY MICHAEL
• Application Number:
  US12/173,973
• Publication Number:
  US 20080272511A1
• Time in Patent Office: 860 Days
• Field of Search: None
• US Class Current: 264/321
• CPC Class Codes: B29C 2035/0822 using IR radiation
• CPC Class Codes: B29C 2791/001 Shaping in several steps
• CPC Class Codes: B29C 44/569 Shaping and joining components with different densities or hardness
• CPC Class Codes: B29C 48/0011 combined with compression moulding
• CPC Class Codes: B29C 48/0012 combined with shaping by internal pressure generated in the material, e.g. foaming
• CPC Class Codes: B29C 48/0017 combined with blow-moulding or thermoforming
• CPC Class Codes: B29C 48/12 Articles with an irregular circumference when viewed in cross-section, e.g. window profiles
• CPC Class Codes: B29C 51/12 of articles having inserts or reinforcements
• CPC Class Codes: B29C 51/165 combined with the feeding or the shaping of the lining or the labels by injection moulding B29C45/14008, B29C45/1418
• CPC Class Codes: B29C 51/427 Cooling of the material with a fluid blast
• CPC Class Codes: B29C 65/02 by heating, with or without pressure
• CPC Class Codes: B29C 65/08 using ultrasonic vibrations non-plastics element to plastics elements B29C65/645
• CPC Class Codes: B29C 65/10 using hot gases (e.g. combustion gases) or flames coming in contact with at least one of the parts to be joined
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• CPC Class Codes: B29C 66/433 Casing-in, i.e. enclosing an element between two sheets by an outlined seam for bookbinding B42C11/06; for packaging B65B; by laminating B32B37/00; enclosing tubular articles between substantially flat elements B29C66/53261
• CPC Class Codes: B29C 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/727 being porous, e.g. foam
• CPC Class Codes: B29C 66/7315 Mechanical properties
• CPC Class Codes: B29C 66/73151 Hardness
• CPC Class Codes: B29C 66/73921 characterised by the materials of both parts being thermoplastics
• CPC Class Codes: B29C 66/8242 : Pneumatic or hydraulic drives using fluid pressure directly acting on the parts to be joined B29C66/8266
• CPC Class Codes: B29C 66/8322 : Joining or pressing tools reciprocating along one axis
• CPC Class Codes: B29C 66/83221 : cooperating reciprocating tools, each tool reciprocating along one axis
• CPC Class Codes: B29C 66/91411 : of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29C 66/91645 : by steps
• CPC Class Codes: B29C 66/91931 : in explicit relation to the fusion temperature or melting point of the material of one of the parts to be joined
• CPC Class Codes: B29K 2023/04 : Polymers of ethylene
• CPC Class Codes: B29K 2023/06 : PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/0633 : LDPE, i.e. low density polyethylene
• CPC Class Codes: B29K 2023/065 : HDPE, i.e. high density polyethylene
• CPC Class Codes: B29K 2023/10 : Polymers of propylene
• CPC Class Codes: B29K 2023/12 : PP, i.e. polypropylene
• CPC Class Codes: B29K 2025/04 : Polymers of styrene
• CPC Class Codes: B29K 2025/06 : PS, i.e. polystyrene
• CPC Class Codes: B29K 2025/08 : Copolymers of styrene, e.g. AS or SAN, i.e. acrylonitrile styrene B29K2055/02 takes precedence
• CPC Class Codes: B29K 2067/00 : Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2069/00 : Use of PC, i.e. polycarbonates or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2071/12 : PPO, i.e. polyphenylene oxide; PPE, i.e. polyphenylene ether
• CPC Class Codes: B29K 2105/04 : cellular or porous
• CPC Class Codes: B29K 2995/007 : Hardness
• CPC Class Codes: B29K 2995/0089 : Impact strength or toughness
• CPC Class Codes: B29L 2009/00 : Layered products
• CPC Class Codes: B29L 2031/7178 : Pallets
• CPC Class Codes: B65D 19/0018 : and each contact surface having a discrete foot-like shape
• CPC Class Codes: B65D 2519/00034 : Plastic
• CPC Class Codes: B65D 2519/00069 : Plastic
• CPC Class Codes: B65D 2519/00273 : made of more than one piece
• CPC Class Codes: B65D 2519/00288 : made of one piece
• CPC Class Codes: B65D 2519/00318 : made of one piece
• CPC Class Codes: B65D 2519/00338 : contact surface having a discrete foot-like shape
• CPC Class Codes: B65D 2519/00562 : chemical connection, e.g. glued, welded, sealed
• CPC Class Codes: B65D 2519/00835 : Integral

Abstract

Load-bearing articles are manufactured from shape defining compressible cores and thermoplastic shells. The manufacture of these articles requires specific methods and tools. Articles that can be manufactured using these methods include relatively lightweight pallets with high load-bearing capacity.

Claims

1. A method of forming articles including a shape defining compressible core member, and a thermoplastic external shell, said method comprising the steps of:

providing a shape defining compressible core member including a first surface and a second surface, wherein at least one surface includes a pattern of features, said core member being comprised of expanded polymer;

positioning said core member adjacent to a first heated pliable thermoplastic sheet that is without a preformed contour, to form a stack including said first sheet and said core member, wherein said first pliable thermoplastic sheet is longer and wider than said core member;

compressing said stack between a first molding tool and a second molding tool, wherein said first molding tool has a surface at least as long and as wide as said core member, and said second molding tool has a surface at least as long and as wide as said core member and a contour complimentary to the features of said at least one surface of said core member, wherein said core member is used as a plug assist to move said sheet into the contour of said second molding tool when compressing said stack;

holding said stack between said first and said second molding tools until said stack cools and bonds form between portions of said core member and said sheet in contact with one another;

removing said stack from said first and second molding tools, wherein the volume of said core member is greater before said core member is compressed between said first and said second molding tools than the volume of said core member after said stack is removed from said first and second molding tools and

wherein said core member has an uncompressed volume that is greater than a volume of a space formed by closure of said first and second molding tools.

2. The method according to claim 1, further including the steps of:

providing a perforated first surface for said interior of surface of said second molding tool; and

supplying vacuum to perforations in an interior of said first surface of said second molding tool such that said vacuum can be used to draw and hold said thermoplastic sheet into close contact with the contour of said perforated first surface of said second molding tool.

3. The method according to claim 1, wherein the distance between said first and said second molding tools is decreased by moving said first molding tool towards said second molding tool.

4. The method according to claim 1, wherein the distance between said first and said second molding tools is decreased by moving said second molding tool towards said first molding tool.

5. The method according to claim 1, wherein said expanded polymer of said core member comprises a compressible material selected from the group consisting of:

Polystyrene (PS), a blend of polyphenylene ether (PPE) and polystyrene (PS) impregnated with pentane, a blend of polyphenylene ether (PPE) and polystyrene (PS) impregnated with pentane, Polyethylene (PE) and Polypropylene (PP).

6. The method according to claim 1, wherein said first thermoplastic sheet has a thickness from about 0.04 inches to about 0.08 inches.

7. The method according to claim 1, wherein said core member and said first thermoplastic sheet comprise chemically compatible materials that bond to one another when said materials are heated and held in contact with one another.

8. The method according to claim 1, including the step of,

providing a second heated pliable thermoplastic sheet, wherein said second sheet is introduced into said process in an orientation substantially parallel to the orientation of said first thermoplastic sheet so as to sandwich said core member between said first sheet and said second sheet forming said stack, compressing said stack and holding said stack between said first and second molding tools until said stack cools and bonds form between portions of said core member and said second sheet in contact with one another.

9. The method according to claim 8, wherein said first and said second sheets continue to compress said core member as said stack cools and said thermoplastic sheets contract.

10. The method according to claim 8, wherein heat transferred from said first and said second heated sheets to the core member promotes bonding between the surfaces of said core member and said first and said second sheets.

11. The method according to claim 8, wherein said thermoplastic sheets comprise a thermoplastic material selected from the group consisting of:

Polypropylene/Polypropylene composite, Polycarbonate (PC), High Impact Polystyrene (HIPS), Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polypropylene (PP), and Polyphenylene Ether alloyed with High Impact Polystyrene.

12. The method according to claim 8, including the step of:

coating said core member with a thermo-activated adhesive before compressing said stack.

13. The method according to claim 8, wherein said core member and said first and said second thermoplastic sheets comprise chemically compatible materials that bond to one another when said materials are heated and held in contact with one another.

14. The method according to claim 8, wherein said core member comprises Expanded Polypropylene (EPP) and said first and said second thermoplastic sheets comprise thermoplastic olefin (TPO).

15. The method according to claim 14, wherein said TPO further includes talc, calcium carbonate, and pressing aids.

16. The method according to claim 14, wherein said TPO is about 0.04 to about 0.08 inches thick.

17. The method according to claim 14, wherein said first sheet of TPO is about 0.08 inches thick and said second sheet of TPO is about 0.04 inches thick.

18. The method according to claim 14, wherein said first and said second sheets are about 0.04 inches thick.

19. The method according to claim 14, wherein said EPP has a density ranging from about 1.9 to about 5.0 pounds per cubic foot (lbs./ft.³).

20. The method according to claim 14, wherein said EPP has a density of about 1.9 pounds per cubic foot (lbs./ft.³).

21. The method according to claim 14, wherein said core member is shaped by steam chest molding before said core member is provided to form said article.

22. The method according to claim 1, further including the steps of:

providing a first clamping frame and a second clamping frame wherein both said first and said second clamping frames are larger than said first and said second molding tools;

attaching said heated first thermoplastic sheet to said first clamping frame;

carrying out said compressing step;

attaching a heated second thermoplastic sheet to said second clamping frame;

positioning said second sheet between said first molding tool and said core member;

compressing said stack that includes said core sandwiched between said first sheet and said second sheet; and

holding said stack between said first and said second molding tools until said stack cools and bonds form between portions of said core member and said second sheet in contact with one another.

23. A method of forming articles comprising the steps of:

providing a compressible core member that includes a first surface and a second surface, wherein said second surface of said core member includes a contour;

providing a heated thermoplastic sheet adjacent said core member, said sheet being without a preformed contour;

positioning said core member and said sheet between first and second molding tools;

wherein said second molding tool has a contour that is complementary to the contour of said core member and said core member has an uncompressed volume that is greater than a volume of a space formed by closure of said first and second molding tools;

compressing said core member and said sheet together between said first and second molding tools, wherein said core member is used as a plug assist to move said sheet into the contour of said second molding tool and wherein the core member is compressed to a compressed volume that is received by the volume of the space formed by closure of said first and second molding tools;

holding said core member and said sheet between said first and said second molding tools until said core member and said sheet cool and bonds form therebetween; and

removing said sheet and said core member from said first and second molding tools, wherein the volume of said core member is greater before said core member is compressed between said first and said second molding tools than the volume of said core member after said core member and said sheet are removed from said first and second molding tools.

24. The method of claim 23 further comprising:

positioning a heated second thermoplastic sheet between said first molding tool and said core member;

compressing said core member and said first and second sheets between said first and second molding tools; and

holding said core member and said first and second sheets between said first and said second molding tools until said core member and said first and second sheets cool and bonds form therebetween.

25. The method according to claim 23, wherein said thermoplastic sheet has a thickness from about 0.04 inches to about 0.08 inches.