Thread forming apparatus and method for rotationally molded product

Patent metadata

Field	Value
Publication number	US-11224998-B2
Application number	US-201715401863-A
Country	US
Kind code	B2
Filing date	Jan 9, 2017
Priority date	Jan 14, 2016
Publication date	Jan 18, 2022
Grant date	Jan 18, 2022

Abstract

A thread forming apparatus for forming threads in a rotational molding apparatus comprising a molding pin having a generally elongate shape, at least a portion of the molding pin having a threaded portion, the molding pin adapted to rotate along with the mold and receive the plastic material on at least the threaded portion, the molding pin being releasable relative to the mold such that once the plastic material coats the threaded portion of the molding pin and forms a threaded portion on the molded product, the molding pin is completely removed from the mold.

First claim

The invention claimed is:

1. A method of forming threads in a rotationally molded product using a rotational molding apparatus that includes a mold held in a molding chamber, the method comprising:
rotating the mold while connected to a thread forming apparatus and in the molding chamber, the thread forming apparatus defining a central longitudinal axis and including a molding pin and a sleeve, the sleeve secured to the mold and including an opening for receiving the molding pin and a sleeve portion positioned outside of the mold, the molding pin including a threaded portion positioned to extend into the mold, the threaded portion of the molding pin having a width, defined in a direction perpendicular to the central longitudinal axis, that is less than a width of the sleeve portion positioned outside of the mold;
providing a plastic material in a solid form within the molding chamber; and
supplying heat in the molding chamber to at least heat the threaded portion of the molding pin to coat the mold and at least the threaded portion of the molding pin with the plastic material and thereby form a molded product having a molded product body conforming to the shape of the mold and a threaded portion of the molded product conforming to the shape of the threaded portion of the molding pin, the threaded portion of the molded product formed simultaneously when the molded product body is formed, the conforming of the threaded portion of the molded product to the threaded portion of the molding pin providing the threaded portion of the molded product complementary to the threaded portion of the molding pin such that the threaded portion of the molding pin threadingly engages with the threaded portion of the molded product and such that the threaded portion of the molding pin is releasable from the threaded portion of the molded product by unthreading the molding pin from the molded product, whereby the threaded portion of the molded product remains after release of the molding pin.

2. The method of claim 1 , further comprising applying an impact torque to an end of the molding pin to unthread the molding pin from the molded product.

3. The method of claim 1 , further comprising reusing the molding pin to form another molded product having a threaded portion after disengaging the molding pin from the mold.

4. The method of claim 1 , wherein the molding pin comprises a hollow body portion and the threaded portion, whereby the hollow body portion facilitates heat conduction in a radial direction toward an outer surface of the molding pin.

5. The method of claim 1 , wherein the threaded portion of the molding pin is releasable from the threaded portion of the molded product via a portion of the thread forming apparatus that is positioned exterior to the mold before the rotating the mold, before the providing the plastic material, and before the supplying heat.

6. The method of claim 1 , wherein the molding pin comprises an elongated core extending a length outward from the threaded portion, and wherein the elongated core is positioned to extend into the mold.

7. The method of claim 6 , wherein the elongated core includes a material configured to prevent the plastic material from covering an end of the molding pin proximal to the threaded portion.

8. A method of forming threads in a rotationally molded product using a rotational molding apparatus, the method comprising:
rotating at least one of a mold of the rotational molding apparatus and a thread forming apparatus connected to the mold, the thread forming apparatus defining a central longitudinal axis and including a molding pin and a sleeve, the sleeve secured to the mold and including an opening for receiving the molding pin and a sleeve portion positioned outside of the mold, the molding pin including a threaded portion positioned to extend into the mold, the threaded portion of the molding pin having a width, defined in a direction perpendicular to the central longitudinal axis, that is less than a width of the sleeve portion positioned outside of the mold; and
heating at least the threaded portion of the molding pin to coat the threaded portion of the molding pin with a plastic material and thereby form a molded product having a molded product body conforming to the shape of the mold and a threaded portion of the molded product conforming at least in part to the shape of the threaded portion of the molding pin, the threaded portion of the molded product formed simultaneously when the molded product body is formed, the conforming of the threaded portion of the molded product to the threaded portion of the molding pin providing the threaded portion of the molded product complementary to the threaded portion of the molding pin such that the threaded portion of the molding pin threadingly engages with the threaded portion of the molded product and such that the threaded portion of the molding pin is releasable from the threaded portion of the molded product by unthreading the molding pin from the molded product, whereby the threaded portion of the molded product remains after release of the molding pin.

9. The method of claim 8 , further comprising reusing the molding pin to form another molded product having a threaded portion after disengaging the molding pin from the mold.

10. The method of claim 8 , wherein the molding pin comprises an elongated core extending a length outward from the threaded portion, and wherein the elongated core is positioned to extend into the mold.

11. The method of claim 10 , wherein the elongated core also extends into a hollow body of the molding pin, and wherein the elongated core includes a vent configured to provide air exchange with the hollow body of the molding pin.

12. The method of claim 1 , wherein the plastic material coats the mold and the threaded portion of the molding pin at different times.

13. The method of claim 8 , wherein the plastic material coats the mold and the threaded portion of the molding pin at different times.

Assignees

• Tennant Co

Inventors

• Westveld Steven P

Classifications

• B29C41/38

  Moulds, cores or other substrates · CPC title

• B29C41/40 Primary

  Cores · CPC title

• B29K2905/00

  Use of metals, their alloys or their compounds, as mould material · CPC title

• B29L2001/00

  Articles provided with screw threads · CPC title

• B29C41/04

  Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould · CPC title