# US 5,349,169 A · Microwave oven using a precoated sheet steel as walls of an internal chamber thereof

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- Number: US 5,349,169 A
- Document ID: US5349169A
- Status: Granted
- Kind: A
- Application number: 07/942,177
- Filed: 1992-09-09
- Granted: 1994-09-20
- Earliest claimed: 1991-12-27
- Assignees: Sharp Kabushiki Kaisha
- Inventors: Yoshiharu Ueno; Masahiro Inoue
- Web page: https://patentgrep.com/patent/US5349169A

## CPC

- H05B 6/642: {Cooling of the microwave components and related air circulation systems (H05B6/6473 takes precedence)}
- H05B 6/6426: {Aspects relating to the exterior of the microwave heating apparatus, e.g. metal casing, power cord}
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

There is provided a microwave oven using as walls of its internal chamber a precoated sheet steel which has no harmful effect on food sanitation. The precoated sheet steel includes a comprised a sheet steel, a strontium chromate primer having strontium chromate dispersion-mixed with a resin and being applied to one side of the sheet steel, a paint applied over the strontium chromate primer, and a paint applied over the other side of the sheet steel. The one side of the precoated sheet steel constitutes exterior surfaces of the walls of the internal chamber and the other side of the precoated sheet steel constitutes interior surfaces of the walls of the internal chamber. A molybdenum primer comprising molybdenum pigment dispersion-mixed with a resin may be applied to both sides of the sheet steel instead of the strontium chromate primer.

## Claims

### Claim 1

A microwave oven comprising:
an internal chamber having walls comprised of a precoated sheet steel, wherein the precoated sheet steel includes
a sheet steel,
a first paint comprising strontium chromate dispersion-mixed with a resin and being applied to only one side of the sheet steel as a primer, said one side of the precoated sheet steel constitutes exterior surfaces of the walls of the internal chamber,
a second paint applied over the primer, and
a paint which is different than said first paint, applied over the other side of the sheet steel, said other side of the precoated sheet steel constitutes interior surfaces of the walls of the internal chamber; whereby the paints preventing corrosion of the microwave oven walls.

### Claim 2 (depends on 1)

The microwave oven as set forth in claim 1, wherein a proportion of strontium chromate in a composition of the primer after baking of the primer is not less than 20 wt %.

### Claim 3

A microwave oven comprising:
an internal chamber having walls of a precoated sheet steel, wherein the precoated sheet steel includes
a sheet steel,
a paint comprising molybdenum pigment dispersion-mixed with a resin and being applied to both sides of the sheet steel as a primer, and
paints applied over the primer of the both sides of the sheet steel wherein the sheet steel is an iron/zinc alloy plated, surface treated sheet steel.

### Claim 4

A microwave oven comprising:
an internal chamber having walls of a precoated sheet steel, wherein the precoated sheet steel includes
a sheet steel,
a paint comprising molybdenum pigment dispersion-mixed with a resin and being applied to one side of the sheet steel as a primer,
a paint applied over the primer, and
a paint applied over the other side of the sheet steel wherein the sheet steel is an iron/zinc alloy plated, surface treated steel sheet.