Method and apparatus for molding plastics with elongated metallic cores
AssigneeRotational Molding Technologies, Inc.
InventorCarl W. Van Gilst
Life of this patent
Estimating the term…
Abstract
A rotomolded plastic wall and ladder structure (10, 50, or 58)), which may be an article such as a window well (10) or a manhole (50 or 58), includes a thermoplastic wall (12), a ladder (16) whose rungs (18) each include an elongated metallic core (20) and a thermoplastic sleeve (22). Mold apparatus (70) includes a thermoplastic rotomold (72), an elongated hollow metallic core (20) having a heating passage (74) therein, and means for flowing hot air through the heating passage (74). The method includes disposing the hollow metallic core in a mold, placing a quantity of a thermoplastic inside a mold, heating the mold, rotating the heated mold, flowing heated air through the hollow metallic core, and bonding a layer of the thermoplastic onto the hollow metallic core.
Claims17
A method for rotomoiding a thermoplastic article which comprises placing a quantity of a thermoplastic inside a rotomold, heating said rotomold, and rotating said heated rotomold, the improvement which comprises:
- a) disposing at least a portion of a metallic core, that includes a heating passage, in said rotomold;
- b) flowing heated air through said heating passage during at least a portion of time wherein said rotating step is performed;
- c) bonding a layer of said thermoplastic onto said metallic core during at least a portion of said rotating step;
- d) said disposing step comprises providing a pair of openings through said rotomold, and clamping said metallic core with respect to said rotomold;
- and
- e) said flowing step comprises communicating said heated air through one of said openings and into said heating passage, and communicating said heated air from said heating passage through the other of said openings to air outside said rotomold.
A method for rotomolding a thermoplastic article which comprises placing a quantity of a thermoplastic inside a rotomold, heating said rotomold, and rotating said heated rotomold, the improvement which comprises:
- a) disposing at least a portion of a metallic core, that includes a heating passage, in said rotomold;
- b) flowing heated air through said heating passage during at least a portion of time wherein said rotating step is performed;
- c) bonding a layer of said thermoplastic onto said metallic core during at least a portion of said rotating step;
- d) said disposing step comprises providing first and second openings in said rotomold, inserting first and second clamp bars through respective ones of said openings, and clamping said metallic core between said clamp bars;
- and
- e) said flowing step comprises communicating said heated air into one of said clamp bars and out of another of said clamp bars.
Mold apparatus (70) for rotationally molding thermoplastic articles which comprises:
- a rotomold (72) having a pair of openings (98) therethrough;
- an elongated metallic core (20) having a heating passage (74) therein, ends (106) and being at least partially disposed inside said rotomold;
- a clamp bar that includes a longitudinal passage (88) and that extends through said openings to clamp said ends of said metallic core with respect to said rotomold such that said longitudinal passage (88) is in communication with said heating passage (74);
- and
- a hot air passage that includes an inlet port (78), said heating passage (74), said longitudinal passage (88) and a transverse passage (110) that communicates air from one of said openings into said heating passage and from said heating passage through another of said openings to air outside said rotomold.
Dependencies are inferred from the claim text.