Method of molding a lined plastic storage tank
AssigneeInfiltrator Water Technologies, LLC
InventorsPaul R. Holbrook, Roy E. Moore, JR., Bryan A. Coppes
Life of this patent
Estimating the term…
Abstract
A method of making a plastic tank suitable for containing water comprises forming a tank base which is partially or fully lined with a plastic layer that is different in character or color from the plastic material of the substrate of the tank base. The tank is alternatively formed by injection molding substrate material around the core of a mold which is partially or fully covered by the liner material, and by injecting liner material into the mold to bond it to the tank base substrate in conjunction with retracting part or all of the core, to provide space in the mold for the liner material.
Claims16
A method of making a plastic water storage tank which comprises injection molding, with use of a mold comprised of a core part and a cavity part, at least a portion of a tank base having a side wall and a bottom wall which in combination define a tank concavity, wherein the base of the tank is shaped for nesting within like tank bases and each said wall of the base comprises a substrate in combination with a liner made of material which is different from the material of the substrate and wherein the liner forms the interior surface of the concavity, the method characterized by:
- (a) surrounding at least the side wall-defining portion of the mold core with a film of first thermoplastic material;
- (b) inserting the core within the mold cavity to define between the core and cavity a mold space that is suited for injection of thermoplastic, wherein the core is shaped to define the interior of the side wall and bottom of said tank base, and the mold cavity is shaped to define the exterior surface of the tank base;
- and,
- (c) injecting a second thermoplastic into said mold space thereby to form the substrate of the tank base and to cause attachment of said film, as a first portion of said liner, to at least that portion of the substrate that comprises the side wall of the tank base;
- (d) then partially withdrawing the core or an end part of the core from the mold cavity, so that the core or the end part of the core moves away from the portion of substrate which forms the bottom wall of the base, to create an void space between the substrate forming said bottom and the moved portion of the core;
- (e) injecting thermoplastic material into said void space so that the plastic material attaches to the bottom wall of the substrate and to the film which is the first portion of the liner, thereby to form a second portion of liner contiguous with the first portion;
- and,
- (f) withdrawing the mold core entirely from the mold cavity and removing the tank base from the mold cavity.
A method of making a plastic water storage tank which comprises injection molding, with use of a mold comprised of a core part and a cavity part, at least a portion of a tank base having a side wall and a bottom wall which in combination define a tank concavity, wherein the base of the tank is shaped for nesting within like tank bases and each said wall of the base comprises a substrate in combination with a liner made of material which is different from the material of the substrate and wherein the liner forms the interior surface of the concavity, the method characterized by:
- (a) inserting the core within the mold cavity to define between the core and cavity a mold space that is suited for injection of thermoplastic, wherein the core is shaped to define the interior of the side wall and bottom of said tank base, and the mold cavity is shaped to define the exterior surface of the tank base;
- and,
- (b) injecting a thermoplastic into said mold space thereby to form the substrate of the tank base;
- (c) then partially withdrawing the core or an end part of the core from the mold cavity, so that the core or end part moves away from the portion of substrate which forms the bottom wall of the base, to create a void space between the substrate forming said bottom the moved portion of the core;
- (d) injecting thermoplastic material into said void space so that the thermoplastic material attaches to the bottom wall of the substrate as a liner portion;
- and,
- (e) withdrawing the mold core from the mold cavity and removing the tank base from the mold cavity.
A method of making a plastic water storage tank which comprises injection molding, with use of a mold comprised of a core part and a cavity part, at least a portion of a tank base having a side wall and a bottom wall which in combination define a tank concavity, wherein the base of the tank is shaped for nesting within like tank bases and each said wall of the base comprises a substrate in combination with a liner made of material which is different from the material of the substrate and wherein the liner forms the interior surface of the concavity, the method characterized by:
- (a) surrounding the mold core which defines the interior concavity of the base with a film of first thermoplastic material;
- (b) inserting the core within the mold cavity to define a mold space between the core and cavity that is suited for injection of thermoplastic, wherein the core is shaped to define the interior of the side wall and bottom of said tank base, and the mold cavity is shaped to define the exterior surface of the tank base;
- and,
- (c) injecting a second thermoplastic into said mold space thereby to form the substrate of the tank, and cause attachment of said film to at least the portion of the substrate that forms the side wall of the base;
- wherein, the mold core is surrounded by the film in step (a) by providing the film as a sheet outside the mold cavity, which sheet runs transverse to the direction in which the core moves for positioning within the mold cavity;
- and moving the mold core against and into the sheet, to cause the sheet to drape around the mold core either before the mold core enters the mold cavity or as the mold core enters the mold cavity;
- wherein the first thermoplastic material comprising the substrate is a recycled plastic material comprised of polyethylene or polypropylene;
- wherein the film is virgin polyethylene or virgin polypropylene material;
- and, wherein the substrate material is black or blue in color and the film material is either white or is a lighter color than the color of the substrate.
Dependencies are inferred from the claim text.