Process and device for preheating moulds

Claim 2

In a process for the steam moulding of parts from expanded thermoplastic material in a mould having a mould cavity defined by walls comprising a wall having a plurality of orifices which put the cavity in communication with a steam chamber to ensure a substantially even distribution of steam in the cavity; the improvement characterized by: preheating the walls of the cavity prior to the supply of steam to said chamber for moulding, by supplying hot air to said chamber which air enters said cavity by way of said orifices.

Claim 3

A moulding press for moulding parts from expanded thermoplastic material by putting steam in contact with said material, comprising in combination: a mould having walls defining a mould cavity, a steam chamber adjoining a wall of the mould cavity, a plurality of throughway orifices in said wall arranged substantially throughout said wall for distributing steam from said chamber in said cavity, a source of steam, a source of hot air, inlet means putting said chamber in communication with said steam source and with said hot air source, first valve means combined with said inlet means for permitting first the supply of hot air to said chamber to preheat the mould cavity walls prior to the supply of steam to said chamber and thereafter the supply of steam to said chamber, outlet means for connecting said chamber to a discharge and second valve means controlling said outlet means.

Claim 4

A moulding press for moulding parts from expanded thermoplastic material by putting steam in contact with said material, comprising in combination: a mould having walls defining a mould cavity, a steam chamber adjoining a wall of the mould cavity, a plurality of throughway orifices in said wall arranged substantially throughout said wall for distributing steam from said chamber in said cavity, a source of steam, a source of hot air, inlet means putting said chamber in communication with said steam source and with said hot air source, first valve means combined with said inlet means for permitting first the supply of hot air to said chamber to preheat the mould cavity walls prior to the supply of steam to said chamber and thereafter the supply of steam to said chamber, outlet means for connecting said chamber to a discharge and second valve means controlling said outlet means.

Claim 5

A press as claimed in claim 2, comprising a valve connected to each of said orifices, each valve having a double input for selective connection of the orifices to a hot air supply source and to a steam supply source.

Claim 6

A press as claimed in claim 2, wherein the mould is constituted by two semi-moulds which are movable with respect to each other, each semi-mould having a wall with a plurality of steam-distributing orifices and defining a part of the mould cavity, there being two of said steam chambers respectively adjoining the two walls with said orifices and communicating with the mould cavity via said orifices, each chamber having said inlet means, said first valve means, said outlet means and said second valve means.