Insulating material, electrical heating unit employing same, and manufacturing method therefor

An electrical heating unit having

• a heat insulating material having an outer layer comprising mainly refractory inorganic fiber;
• a core layer supported within and joined to the outer layer;
• and
• a groove formed in one surface of the outer layer and at least part of the heating element is embedded in the bottom of the groove, so as to be joined and supported therewith,
• wherein the outer layer has a substantial thickness and greater mechanical strength than the core layer, the core layer comprises a composition having a greater insulating performance than the outer layer, and the core layer extends in a place substantially perpendicular to the thickness of the heat insulating material.

A method for manufacturing a heat insulating material as a single unit comprising the steps of:

• building up under compressive force a first heat insulating layer comprising mainly refractory inorganic fiber;
• positioning on the first heat insulating layer a core layer comprising a composition with a better insulating performance than said first heat insulating layer and having dimensions smaller than the first heat insulating layer;
• and
• building up under compressive force a second heat insulating layer comprising mainly refractory inorganic fiber so that the core layer is completely enclosed and supported therein.

A method for manufacturing an electrical heating unit as a single unit comprising the steps of:

• building up under compressive force a first heat insulating layer comprising mainly refractory inorganic fiber,
• at least partially embedding a heating element near a surface of the first heat insulating layer
• positioning on the first heat insulating layer a core layer comprising a composition with a better insulating performance than said first insulating layer and having dimensions smaller than the first heat insulating layer;
• and
• building up under compressive force a second heat insulating layer comprising mainly refractory inorganic fiber so the core layer is enclosed.

A single unit heat insulating material made by the steps comprising:

• building up under compressive force a first heat insulating layer comprising mainly refractory inorganic fiber;
• positioning on the first heat insulating layer a core layer comprising a composition with a better insulating performance than said first heat insulating layer and having dimensions smaller than the first heat insulating layer;
• and
• building up under compressive force a second heat insulating layer comprising mainly refractory inorganic fiber so that the core layer is completely enclosed and supported therein.

An electrical heating unit made by the steps comprising:

• building up under compressive force a first heat insulating layer comprising mainly refractory inorganic fiber;
• embedding at least part of a heating element in the first heat insulating layer,
• positioning on the first heat insulating layer a core layer comprising a composition with a better insulating performance than said first heat insulating layer and having dimensions smaller than the first heat insulating layer;
• and
• building up under compressive force a second heat insulating layer comprising mainly refractory inorganic fiber so that the core layer is completely enclosed and supported therein.