Heating apparatus for cooking food, especially a hot plate

• US 5,183,997 A
• Filed: 09/18/1991
• Issued: 02/02/1993
• Est. Priority Date: 03/21/1989
• Status: Expired due to Fees

• Current Assignee: Balzers und Leybold Deutschland Holding AG (Balzers & Leybold Group)
• Original Assignee: Leybold Aktiengesellschaft
• Inventors: Lotz, Hans-Georg
• Primary Examiner(s): Walberg, Teresa J.
• Application Number:
  US07/762,012
• Time in Patent Office: 503 Days
• Field of Search: 219/443, 219/458, 219/459, 219/461, 219/462, 219/464, 219/465
• US Class Current: 219/460.1
• CPC Class Codes: C03C 17/3482 comprising silicon, hydrogenated silicon or a silicide
• CPC Class Codes: H05B 3/744 Lamps as heat source, i.e. heating elements with protective gas envelope, e.g. halogen lamps

Abstract

Heating apparatus which emits optical radiation having a visible content and an infrared content, for cooking foods by means of at least one radiation source (2) directed at a cook site for accommodating foods to be cooked or a container for foods to be cooked. Between the radiation source (2) and the cook site (4) there is a filter (7) having a support body (8) made of a material that is substantially permeable for all of the radiation. The support body (8) is provided with an interference layer system which reflects the visible content of the radiation at least predominantly to the radiation source and passes the infrared content of the radiation at least predominantly to the cook site. In order to achieve a simpler, firmly adherent layer build up with a small number of layers and without inner tensions, the interference layer system (9) consists of an alternating sequence of layers of silicon (H) and silicon dioxide of silicon (H) and silicon dioxide (N), whose physical layer thicknesses in the case of the silicon, at least in the predominant part of the silicon layers, are between 20 and 50 nanometers, and in the case of the SiO₂ are between 80 and 110 nm, at least in the predominant part of the SiO₂ layers.

Claims

1. Heating apparatus for cooking foods comprising at least one radiation source directed at a cook site for accommodating food to be cooked or a container for food to be cooked, said source emitting optical radiation with a visible content and an infrared content, a filter with a support body made of a material substantially transparent to the radiation, said filter being disposed between the radiation source and the cook site and provided with an interference layer system which reflects the visible content of the radiation at least predominantly to the radiation source and passes the infrared content of the radiation at least predominantly to the cook site, wherein the interference layer system comprises an alternating series of layers of silicon (H) and silicon dioxide (N) whose physical layer thicknesses in the case of the silicon is between 20 and 50 nm, and in the case of the SiO₂ between 80 and 110 nm.

2. Heating apparatus according to claim 1, wherein at least three layer pairs H/N are provided.

3. Heating apparatus according to claim 2, wherein five layer pairs H/N are provided.

4. Heating apparatus according to claim 3, wherein the physical layer thicknesses from the first to the tenth layer N10 are chosen as follows:

H1=24 nm, N2=92 nm, H3=39 nm, N4=93 nm, H5=39 nm, H6=93 nm, H7=93 nm, N8=93 nm, H9=10 nm, N10=119 nm.

5. Heating apparatus according to claim 2, wherein the layer sequence, starting from the support body (8), begins with a layer of Si.

6. Heating apparatus according to claim 2, wherein the layer sequence ends with a layer of SiO₂.

7. Heating apparatus according to claim 1, wherein the support body consists of an infrared transmitting glass ceramic material and is configured with the interference layer system as a hot plate.

8. Heating apparatus according to claim 7, wherein the support body has a bottom on which the interference layer system (9) is disposed.

9. Heating apparatus according to claim 7, wherein the hot plate has a plurality of placement surfaces for cooking containers and is provided with a masking element at least largely opaque to optical radiation, by which infrared transmitting surface areas defining the placement surfaces within the hot plate are distinguished from radiation opaque surface areas.

10. Heating apparatus according to claim 9, wherein the infrared transmitting surface areas are disposed as circular openings within the masking element.

11. Heating apparatus according to claim 1, wherein, the interference layer system has such a spectral transmission characteristic that said system is transparent to a portion of the radiation in the visible red range.

12. Heating apparatus according to claim 1, wherein the interference layer system has a transmittance range for the infrared radiation which begins at a wavelength of 750 nm.