Thermal valve gate for plastic molding apparatus
US4922082A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 17, 1989 |
| Grant date | May 1, 1990 |
| Priority date | — |
| Expiry date | Mar 17, 2009 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C2045/2746
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
An ohmically or electrothermally controlled valve gate for injection molding apparatus comprises three concentrically located tubes in intimate contact with each other. The innermost tube is an electrode and also serves as the passage for flowing molding material. The outermost of the three tubes is also an electrode. The intermediate tube is a resistive heating element comprising a mixture of at least two highly compacted powders. One powder is an electrical conductor, while the other powder, which serves as a binder for the first powder, is an electrical insulator but a good thermal conductor. Current flow between the electrodes occurs at points of contact between adjacent particles of the conductive powder. Thus, the electrical resistance and therefore the generation of heat is controlled by the composition and quantity of binder in the heating element. The generated heat is conducted through the inner electrode tube to the flowing plastic to melt the plastic and "open" the gate. Interruption or reduction of current flow reduces the heat and permits the plastic in the passage to freeze, thereby "closing" the gate.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.