Rotational molding apparatus

• US 4,102,624 A
• Filed: 10/14/1976
• Issued: 07/25/1978
• Est. Priority Date: 10/14/1976
• Status: Expired due to Term

• Current Assignee: Windsurfing International Incorporated
• Original Assignee: Windsurfing International Incorporated
• Inventors: Corona, Peter J.
• Primary Examiner(s): Spicer, Jr., Robert L.
• Application Number:
  US05/732,267
• Time in Patent Office: 649 Days
• Field of Search: 425/429, 425/430, 425/434, 425/435, 425/454, 264/311, 264/310
• US Class Current: 425/429
• CPC Class Codes: B29C 33/34 movable, e.g. to or from the moulding station
• CPC Class Codes: B29C 41/06 about two or more axes

Abstract

An apparatus and process is disclosed for rotational molding. Rotational molding is a technique for the fabrication of parts from powdered thermoplastic material in which the thermoplastic material is placed within a hollow mold and the mold is rotated in a heated environment until the thermoplastic material fuses and coats the entire interior surface of the mold. Included in the apparatus is a holding mechanism for the mold and a power mechanism to provide the required rotational motion to the mold. The power mechanism provides for simultaneous rotation of the mold about two orthogonal axes and is displaced spatially from the holding mechanism. The holding mechanism is attached to a translating mechanism which positions the molds both internal to and external to a heating chamber such as an oven while keeping the drive mechanism external of the oven at all times.

More specifically there is disclosed an apparatus which includes a truck mounted upon a guiding track and having extending therefrom an arm mechanism. The arm is pivotally attached to the truck and is coupled thereto in such a manner that the arm may be translated about the pivotal point through a vertical path from a horizontal position at a loading/unloading (mold rework) station through approximately 180° to be positioned into a heating chamber at a heating station and a cooling chamber or tower at a cooling station for fabrication of the molded part. Subsequently, thereto the mold attached to the arm may be repositioned at the mold rework station for the removal of the plastic part from the mold. Automatic control mechanisms and interlocks are provided to enable safety measures to be exercised to prevent movement of the truck along the track except at specified times and when the arm is in appropriate position to clear the oven and cooling towers.

Claims

1. A rotational molding apparatus which comprises:

a. a holding mechanism for receiving a mold;

b. a drive means for imparting rotational motion to said holding mechanism;

c. a support structure;

d. pivot means for attaching said holding mechanism and said drive means to said support structure;

e. an oven; and

f. means for rotating said holding mechanism and said drive means about said pivot means along a vertically disposed plane from a position wherein said molding mechanism and said drive means are external to said oven to a position wherein said molding mechanism is internal of said oven and said drive means is external to the oven.

2. The apparatus of claim 1 wherein the holding mechanism comprises:

a. a rotatably mounted extension which engages with said drive mechanism;

b. an arm which connects to said extension;

c. an attachment means rotatably mounted at the terminus of said arm; and

d. means by which rotational energy is transmitted to said attachment means.

3. The apparatus of claim 2 wherein the holding mechanism further comprises:

a. said extension being hollow;

b. said arm being hollow; and

c. means for transmitting rotational motion through said hollow extension and hollow arm to said rotatably mounted attachment means.

4. The apparatus of claim 3 wherein the holding mechanism further comprises:

a. a second arm connected to said extension; and

b. a rotatably mounted attachment means at the terminus of said second arm.

5. The apparatus of claim 3 wherein the drive means comprises:

a. means for generating and transferring rotational motion to said extension; and

b. means for generating and transferring rotational motion to said transmitting means contained within said hollow extension and hollow arm.

6. The apparatus of claim 1 wherein said oven further comprises:

a. means through which the holding mechanism can be inserted;

b. means to provide a seal subsequent to insertion of the holding mechanism.

7. The apparatus of claim 6 wherein said means to provide a seal comprises a moveable door with an aperture through which said extension passes.

8. The apparatus of claim 7 which further comprises a cooling means.

9. The apparatus of claim 8 which further comprises:

a. means for guiding said support structure between said cooling means and said oven.

10. The apparatus of claim 3 wherein said holding mechanism further comprises:

a. a plurality of arms attached to said extension;

b. attachment means rotatably mounted at the terminus of each said arm;

c. means for transmitting rotational motion to at least one of said attachment means.

11. The apparatus of claim 10 wherein said pivot means comprises:

a. first and second pivots to pivot said support structure, drive means and drive means mount as a single entity.

12. The apparatus of claim 11 wherein said first pivot means pivots said single entity 90°

in the vertical plane and said second pivot means pivots and single entity and sequentially rotates 90°

in the vertical plane.

13. Apparatus for rotational molding comprising:

a. truck means;

b. arm means including first and second sections, each having first and second ends, first pivot means interconnecting said first ends of said first and second sections, and second pivot means interconnecting said second end of said first section to said truck means;

c. mold receiving means attached at the second end of said second section of said arm means;

d. power transmitting means carried by arm means and connected to said mold receiving means for applying rotational force to molds received in said mold receiving means; and

e. means for rotating said arm means between predetermined positions about said pivot means.

14. The apparatus of claim 13 wherein said arm means is hollow and said power transmitting means extends through said hollow arm means.

15. The apparatus of claim 13 which further includes a power source, means for mounting said power source on said truck means, and means for connecting said power transmitting means to said power source.

16. The apparatus of claim 13 which further includes a heating station and a cooling station and means for moving said truck means between said heating and cooling stations.