US 4,306,856 A · Pre-heating apparatus for a thermoforming machine

Abstract

There is disclosed a pre-heating apparatus for a thermoforming machine for uniformly heating a thermoplastics sheet or plate throughout, the apparatus comprising a first heating section (A), a cooling section (B) and a further heating section (C). Such arrangement ensures that both the outer and inner layers of the thermoplastics sheet or plate (1) are all at the same temperature when the sheet or plate is subjected to a thermoforming process. There is also disclosed a process for pre-heating a thermoplastics sheet or plate prior to subjecting such sheet or plate to a thermoforming process comprising firstly passing a sheet or plate through a heating section, thereafter through a cooling section and finally through a further heating section. The first heating section and the cooling section are preferably arranged vertically and the further heating section being arranged horizontally, the thermoplastics sheet or plate passing upwardly through the first heating section and downwardly through the cooling section.

Claims10

Dependent claims

A pre-heating apparatus for a thermoforming machine for uniformly heating a thermoplastics sheet or plate throughout, such apparatus comprising feed means for advancing the sheet or plate through a series of sections;

a heating section including heating means for supplying heat to the exterior of the sheet or plate, thereby to heat the plate;
the heating means cooperating with the feed means for causing the exterior of the sheet or plate to be heated above the temperature of the interior of the sheet or plate and for then advancing the sheet or plate out of the heating section;
a cooling section following the heating section and adapted to cool the sheet or plate by cooling the exterior thereof;
the feed means being adapted to advance the sheet or plate out of the cooling section after the exterior of the sheet or plate had cooled to a temperature below the temperature of the interior of the sheet or plate and a further heating section following the cooling section and including further heating means for supplying heat to the exterior of the sheet or plate, thereby to heat the sheet or plate;
the feed means advancing the plate or web through the sections in the recited sequence.

2 more elements

A process for pre-heating a thermoplastics sheet or plate prior to subjecting such sheet or plate to a thermoforming process, comprising firstly passing the sheet or plate through a heating section and supplying heat there to the exterior of the sheet or plate for heating both the exterior and the interior of the sheet or plate;

thereafter passing the sheet or plate through a cooling section for cooling the sheet or plate by cooling the exterior thereof, and retaining the sheet or plate in the cooling section for a period of time sufficient at least to cool the exterior of the sheet or plate with respect to the interior of the sheet or plate such that the positive temperature differential between the exterior and the interior of the sheet or plate is greater in the heating section than in the cooling section, and the period of time being short enough that the interior of the sheet or plate remains heated;
and finally passing the sheet or plate through a further heating section for again supplying heat to the exterior of the sheet or plate, thereby to heat both the exterior and the interior of the sheet or plate to respective higher temperatures.

Dependencies are inferred from the claim text.

Pre-heating apparatus for a thermoforming machine

Life of this patent

Pre-heating apparatus for a thermoforming machine

Life of this patent

Abstract

Claims10